Pros and Cons of Drilled/Slotted rotors

[$$$PIT]

In the near future I will have to put new brakes on my N/A. I have access to a set of VR-4 calipers. If I do this I am contemplating buying drilled/slotted rotors.
The question I have is about reliability and maintenance. I know the performance will be greatly enhanced. This is a DD and I don't usually drive it too hard. But, my philosophy is "I'd rather have it and not need it. Than to need it and not have it".

1. Should I stick with what I have.
2. Upgrade to the VR-4 calipers w/out the drilled/slotted
3. Do it all out.

Your opinions please.

[Austin@STM]

Upgrade to the vr4 calipers, which will be a huge upgrade in performance already, and get a set of good rotors and pads. Maybe brembo blank rotors with some nice hawk pads, with the lighter weight of the N/A it should stop really well. Most people wont really notice or need slotted rotors, its not worth the extra money for a daily driven car. It it was a track car it would be a different story.

-Austin@STM

[Polygon]

Slottled:

Pros:
1. They sweep the pad keep everything nice and clean.
2. They improve the initial bite.

Cons:
1. They are prone to cracking if the slots go all the way to the edges.
2. They will chew up pads faster.
3. As such, expect more brake dust.
4. Cost.

Cross-Drilled:

Pros:
1. Possible bragging rights?

Cons:
1. They will crack.
2. Increased braking distances.
3. Increased probability of fade.
4. Cost.
5. Possible ridicule from people that are in the know about brakes.

Slotting is pretty much a waste of money for a DD that doesn't even drive aggressively. Plus the increased cost. Cross-drilling, on the other is a complete waste of money for anyone. There's a reason that it isn't used in any form of professional racing.

[Austin@STM]

We use a form of cross drilled in drag racing, it make for a very lightweight setup, but very pricey.
The rotor/caliper/lines/hardware together weigh well under 20 pounds.

http://www.streettunedmotorsports.com/parts/b/brake_man_subaru_front.jpg

[DocWalt]

One hard stop isn't quite the same as multiple hard stops :p That setup is friggin nice though man, even if it's only drag racing, hehe. Gonna throw some on the Stealth, or did I not see them?

[Austin@STM]

We actually have a couple cars around here that daily drive wiith those brakes. The loss of rotating mass really helps to.

Back on topic though, if you want some pricing on a good set of rotors and pads, for whichever setup you go with N/A or TT let me know, ill set you up a nice package.

-Austin@STM

[stealthee]

Brake rotors are heat sinks. Remove material from a heat sink and you have an ineffective heat sink.

[Lithium]

Brake rotors are heat sinks. Remove material from a heat sink and you have an ineffective heat sink.

Then what would you say about increasing the surface area? because drilled rotors do increase the surface area of the disk.

[i3igpete]

Then what would you say about increasing the surface area? because drilled rotors do increase the surface area of the disk.

well... that depends on the diameter of the hole and the thickness of the disc.

[Lithium]

well... that depends on the diameter of the hole and the thickness of the disc.

I'm sure the amount of surface area you would gain would be small but just for the sake of an argument.

[$$$PIT]

So, the consensus is VR-4 calipers with regular rotors. I'm thinkin' ceramic pads too.
The only reason I gave the drilled/slotted any thought was for the looks. I have been going to a few car shows and have done well, so far. But, I haven't had that much competition in my class. But, looks only go so far with me. So, I'll listen to you guys.

[Lithium]

VR-4 four pistons are perfect for a daily driven SL.

[Maximal]

If you're just street driving your car go to autozone and get a good mid-grade set of pads and rotors. If you're tracking it then it's a completely different discussion.

Bottom line is slotted (and especially drilled) rotors do more harm than good.

[hotGTO]

Then what would you say about increasing the surface area? because drilled rotors do increase the surface area of the disk.

This is 100% correct! It increases the surface area to increase heat dissipation and also reduces weight... But apparently the general consensus is that they are not good... LOL

Edit: They also wear the pads down less than slotted which is why some people who don't race prefer them...

[Macky]

Cross-drilling, on the other is a complete waste of money for anyone. There's a reason that it isn't used in any form of professional racing.

carbon rotors are drilled, and are used from LeMans to F1 just FYI; while WRC cars still use drilled rotors. ;)

[Macky]

2. Upgrade to the VR-4 calipers w/out the drilled/slotted


Get the 4-piston calipers and a good set of blank rotors and pads. if you are concerned with braking performance on a street car, some better tires (a good set of summer tires ideally) along with the VR4 calipers and regular rotors w/ good pads is all you will really need.

you can have the most aggressive looking brake setup, but if you're riding on cheap tires, you will still have poor braking performance.

[Bob]

I've always heard good reviews on Power Slot rotors. I have a complete set of the old style Power Slots (Stop Tech changed the design and finishes) which are cad plated and have the slots that extend past the edges. My NA is a daily driver and I'm wondering what a good brake pad would be to use with these rotors? I was hoping for less dust, but from what I read here I'll be getting more dust with the Power Slots. I mainly bought them for the appearance.

[hotGTO]

I've always heard good reviews on Power Slot rotors. I have a complete set of the old style Power Slots (Stop Tech changed the design and finishes) which are cad plated and have the slots that extend past the edges. My NA is a daily driver and I'm wondering what a good brake pad would be to use with these rotors? I was hoping for less dust, but from what I read here I'll be getting more dust with the Power Slots. I mainly bought them for the appearance.

Get ceramic pads if you are worried about dust....

[green-lantern]

I really don’t understand the hate with drilled rotors. If they are done correctly they do help. Yes drilled and slotted will wear pads out faster and they can be prone to cracking if it’s a crappy built rotor but I have used drilled rotors in many applications for years and I never had anything happen but better breaking. Every dirt bike I’ve ever owned has had drilled rotors. They also help braking when wet and muddy. All of my railbuggys have had drilled rear rotors. The difference was amazing on the buggy. I’ve used them on my 3000 and found better stopping power. That being said, if I was road racing I would only trust a top quality rotor. I’m not saying I wouldn’t use drilled but I would be much more hesitant to have holes in my rotor when I was getting it red hot over and over again.

[hotGTO]

The hate with the drilled rotors is that they crack under extreme use... Probably a lot of ebay crap being sold and breaking under heavy usage causing a growing wave of people to throw them under the bus... Slotteds are even getting dissed a little due to excessive pad wear and cracking under extreme conditions, but I think it is from the growing number of knockoffs and ebay junk that are being marketed to uninformed drivers as "performance" parts when they are in reality only "show" parts!

Edit: Generally always true is "you get what you pay for" if you buy HIGH quality expensive drilled or slotted rotors, you will probably have good results.

[green-lantern]

The hate with the drilled rotors is that they crack under extreme use... Probably a lot of ebay crap being sold and breaking under heavy usage causing a growing wave of people to throw them under the bus... Slotteds are even getting dissed a little due to excessive pad wear and cracking under extreme conditions, but I think it is from the growing number of knockoffs and ebay junk that are being marketed to uninformed drivers as "performance" parts when they are in reality only "show" parts!

I think you are 100% correct.

[DocWalt]

carbon rotors are drilled, and are used from LeMans to F1 just FYI; while WRC cars still use drilled rotors. ;)
Nope, not drilled. Unless you're counting the venting holes in the F1 brakes.

F1:
http://images.motortrend.com/photo_gallery/112_0702_10z+f1_driving_contest+brakes.jpg

WRC:
http://www.motorsport-sales.com/images/05225752555555.jpg

[R/T93]

My DBA 4000's have begun to crack along the long vanes. Each crack is along a line from the center of the rotor to the edge. They are only about 1/16" long right now

[Lithium]

Here is a real good question, has anyone ever thought about wheels being a big aspect of brake cooling? I have a set of FN01r-c and after a lot of hard driving I could swear my wheels are just as hot as my brakes.

[DocWalt]

They (the wheels) can help draw some heat away, but most of the cooling is needed on the face of the rotor and the caliper to help keep the pad material and brake fluid cool.

[green-lantern]

Here is a real good question, has anyone ever thought about wheels being a big aspect of brake cooling? I have a set of FN01r-c and after a lot of hard driving I could swear my wheels are just as hot as my brakes.

Your brakes could be hanging up or wheel bearings are going out. Just a thought

[ChargerX3]

This thread can use some facts:

http://www.superchargersonline.com/content.asp?ID=98

[Lithium]

They (the wheels) can help draw some heat away, but most of the cooling is needed on the face of the rotor and the caliper to help keep the pad material and brake fluid cool.

They (the wheels) get hot enough that I cannot touch them in fear of getting 2nd degree burns. I'm going to find someone in town with a temp gun to see exactly how hot they (the wheels) actually get. I would almost venture to say brakes could cool better with a larger and wider wheel due to the increased surface area exposed to atmosphere.

[Lithium]

I just installed brand new wheels brearings (3sx) so I would count that out.

[DocWalt]

If they're enough you can't touch them, I'd suggest making sure your brakes aren't dragging.

[Bob]

This thread can use some facts:

http://www.superchargersonline.com/content.asp?ID=98

Good facts. After reading, I feel a little bit better about my Power Slots. :)

[Lithium]

I can easily move the wheels while the brakes are not depressed, I recently restored the front end this past summer. That being said I can say the heat if from braking alone.

[DocWalt]

I have no idea what kind of hard driving you're talking about, but I've never made my wheels so hot I can't touch the wheels at all, and that's including the 3SPA "cruises", lol. I wouldn't want to touch them, but I could have.

[Lithium]

Hard driving = many 120+ to first gear braking sections.

[hotGTO]

http://www.raceshopper.com/tech.shtml#slotted_rotors

[DocWalt]

Hard driving = many 120+ to first gear braking sections.

:suspect: Well yeah, then they'll be damn hot, lol.

[i3igpete]

and before someone mentions the stock brember rotors on GT-R's, be aware that those are drilled just for show. Jack T's rotors at road america last year had spider cracks coming out of EVERY hole. he kept racing on them because he's a nut, but i sure as hell wouldn't.

[Macky]

Nope, not drilled. Unless you're counting the venting holes in the F1 brakes.

F1:
http://images.motortrend.com/photo_gallery/112_0702_10z+f1_driving_contest+brakes.jpg

WRC:
http://www.motorsport-sales.com/images/05225752555555.jpg



my bad on the F1. Im pretty sure I recall seeing cutout views of them showing drilled rotors not too long ago. but Ive personally seen a WRC car that did use drilled steel rotors, Rhys Millen Racing in HB had a Group N Evolution raly car and that used drilled rotors. I used to do their PR work a while back part time.

I think now that all the racing series' have switched to carbon, they got rid of the drilling altogether since heat dissipation and degredation is no longer that much of an issue.

[DocWalt]

All the top level WRC teams use dimpled or slotted rotors, not cross drilled. And IIRC, they haven't switched to carbon because it can't handle the abuse.

[Polygon]

Oh man, there's a lot of bad information in here.

1. There are two ways you can cross-drill a rotor. You use a drill and actually drill the holes. That's how cheap cross-drilled rotors are made and will crack quite easily. Good ones are cast that way. They will still crack, no matter what. If you take any medium and put a bunch of holes in it, it will become weaker.

2. A rotor is a heat sink. It turns mechanical energy into heat energy. So, the rotor needs to be able to contain heat and dissipate it faster than it's absorbing it. If not, you get brake fade. It's simple physics. You remove material from a heat sink you reduce it's ability to hold heat. However, the whole surface area argument is the best one I've heard in cross-drilling's defense as, theoretically, it will fulfill the other half and dissipate the heat faster. While you're correct. That's pretty simple physics as well. However, the gain is marginal at best. The marginal gain is far outweighed by the problems it causes. We could also get into a different kind of surface area as you're actually reducing it as well. I'm talking about the contact patch of the pad on the rotors. It works much like a tire to the road. Less contact patch equals less grip. Yes, that's just as marginal, but it all adds up.

2. Drag racing might use them, why I don't know. But I don't find the fact that they do relevant. I'll rephrase though, no form of road racing uses them anymore. They haven't for a long time. Just like Charger's link posted, cross-drilling was used in racing to prevent out gassing. Modern pads don't out gas, so cross-drilled rotors are useless.



Nope, not drilled. Unless you're counting the venting holes in the F1 brakes.

F1:
http://images.motortrend.com/photo_gallery/112_0702_10z+f1_driving_contest+brakes.jpg

WRC:
http://www.motorsport-sales.com/images/05225752555555.jpg

Thank you!


This thread can use some facts:

http://www.superchargersonline.com/content.asp?ID=98

That is a great article. I'll add it to my other ones.


http://www.raceshopper.com/tech.shtml#slotted_rotors

Well, that's not a great retort as they are making money off selling you those. It's in their best interest to tell you they're better regardless of the fact that it's not true. When someone is trying to sell you something, you should always take it with a grain of salt.

[i3igpete]

Well, that's not a great retort as they are making money off selling you those. It's in their best interest to tell you they're better regardless of the fact that it's not true. When someone is trying to sell you something, you should always take it with a grain of salt.

they also sell big brake kits and race pads. the fact that they say it's not for everyone should be some sort of clue. they could just make more money off big brake kits and shitty street pads (like every super street article tells you to), but the fact is that it's a company run by racers for racers.

[Macky]

All the top level WRC teams use dimpled or slotted rotors, not cross drilled. And IIRC, they haven't switched to carbon because it can't handle the abuse.

ah. must have been an afterthought install then. good info. thanks!

[DocWalt]

ah. must have been an afterthought install then. good info. thanks!

FWIW, they probably change the rotors often enough it doesn't even matter. I've seen pics of rally cars with cross drilled rotors.

[Macky]

possibly. pretty sure that would be one reason the cost of racing is pretty high.

you know what they say, to make a small fortune in racing, you have to start with a large fortune :D

[hotGTO]

Oh man, there's a lot of bad information in here.

I agree with that!



Well, that's not a great retort as they are making money off selling you those. It's in their best interest to tell you they're better regardless of the fact that it's not true. When someone is trying to sell you something, you should always take it with a grain of salt.

I don't agree with that, My whole point in posting that link was to subtly point out that just because a link gives you information does not mean it is always true, thank you for making that point! (I didn't want to be Mr. negative) The info on my link is not just a sales pitch, although I am sure there are plenty that are! As it was already pointed out, that is a race site selling high performance parts to racers, not really a consumer site trying to make money off of selling big brakes... But thanks for the feedback...

[i3igpete]

and regarding the "increases surface area argument". this might not always be true: consider the geometry. you are removing the area of a circle, and adding the circumference of the cylinder. it doesn't take a genius to figure out that with a thin disc, you are removing more surface than you're adding.

really, if you want improved brake cooling performance just add some brake ducts. that is, if you even need them. i mean hell, i only very rarely get brake fade.

[Polygon]

they also sell big brake kits and race pads. the fact that they say it's not for everyone should be some sort of clue. they could just make more money off big brake kits and shitty street pads (like every super street article tells you to), but the fact is that it's a company run by racers for racers.


I agree with that!

I don't agree with that, My whole point in posting that link was to subtly point out that just because a link gives you information does not mean it is always true, thank you for making that point! (I didn't want to be Mr. negative) The info on my link is not just a sales pitch, although I am sure there are plenty that are! As it was already pointed out, that is a race site selling high performance parts to racers, not really a consumer site trying to make money off of selling big brakes... But thanks for the feedback...

Ok, let's get one thing clear and I'm sorry I didn't with my last post. I am IN NO WAY bashing Race Shopper. I've dealt with them on many occasions. They know their shit and they are a great resource. I was more making a statement in general.

Also, the link that Charger posted has a lot of merit as it has the things listed in it have been said a million times before. Even Stop Tech will tell you not to get cross-drilled rotors unless you just have to have them for the looks. Otherwise they say to get slotted instead.

[OhioSpyderman]

Not sure about others, but I like my SEMI-metallic pads. Zero brake dust a great bite (better on the Spyder than the Stealth.....95 calipers VS 92 smaller calipers).

Bob. :)

[Bob]

Not sure about others, but I like my SEMI-metallic pads. Zero brake dust a great bite (better on the Spyder than the Stealth.....95 calipers VS 92 smaller calipers).

Bob. :)

What brand semi-metallic pads are you using? I think the OEM pads are s-m also.

[OhioSpyderman]

What brand semi-metallic pads are you using? I think the OEM pads are s-m also.

To be honest, I can't say...AND if you try to find pads for a 2g AWD 3S, the sources are twindling (my son COULD NOT find ANY pads for his 94VR4 in Toledo....he had to order them online...I had a hard time locating any in Dayton as well...)

I think he finally got some Beck/Arney S/M pads from O'reilly's online...

Bob.

[DocWalt]

I've always ordered my pads online, nobody local has anything worth the money they're asking, IMO.

[Drweldin]

Maybe it's been said, but the only real world advantage is driving in the rain...

[Lithium]

Oh man, there's a lot of bad information in here.

1. There are two ways you can cross-drill a rotor. You use a drill and actually drill the holes. That's how cheap cross-drilled rotors are made and will crack quite easily. Good ones are cast that way. They will still crack, no matter what. If you take any medium and put a bunch of holes in it, it will become weaker.

2. A rotor is a heat sink. It turns mechanical energy into heat energy. So, the rotor needs to be able to contain heat and dissipate it faster than it's absorbing it. If not, you get brake fade. It's simple physics. You remove material from a heat sink you reduce it's ability to hold heat. However, the whole surface area argument is the best one I've heard in cross-drilling's defense as, theoretically, it will fulfill the other half and dissipate the heat faster. While you're correct. That's pretty simple physics as well. However, the gain is marginal at best. The marginal gain is far outweighed by the problems it causes. We could also get into a different kind of surface area as you're actually reducing it as well. I'm talking about the contact patch of the pad on the rotors. It works much like a tire to the road. Less contact patch equals less grip. Yes, that's just as marginal, but it all adds up.

2. Drag racing might use them, why I don't know. But I don't find the fact that they do relevant. I'll rephrase though, no form of road racing uses them anymore. They haven't for a long time. Just like Charger's link posted, cross-drilling was used in racing to prevent out gassing. Modern pads don't out gas, so cross-drilled rotors are useless.




Thank you!



That is a great article. I'll add it to my other ones.



Well, that's not a great retort as they are making money off selling you those. It's in their best interest to tell you they're better regardless of the fact that it's not true. When someone is trying to sell you something, you should always take it with a grain of salt.

I agree with you, the cooling advantages would be very small. To be honest you would be better off installing ducts, I just argue points for the sake of doing so.


:suspect: Well yeah, then they'll be damn hot, lol. I will have to take some temps so we can ponder this some more.

[DocWalt]

I didn't expect your answer of doing 120mph pulls, just spirited driving won't make them that hot. That will, and so will track use.

[Polygon]

I agree with you, the cooling advantages would be very small. To be honest you would be better off installing ducts, I just argue points for the sake of doing so.

It's a great point. I would love to do some. I don't see how it could be that hard. I had mentioned it before to a vendor that was fabbing some stuff but they weren't too interested in the idea. I'm going to give it a try at some point though. Unless someone else does it first.

[Lithium]

It's a great point. I would love to do some. I don't see how it could be that hard. I had mentioned it before to a vendor that was fabbing some stuff but they weren't too interested in the idea. I'm going to give it a try at some point though. Unless someone else does it first.

I'm entertaining the idea but worried about fire hazards, I'm hoping fiberglass will do the trick.

[Polygon]

It should be fine, but if not, the vent at the brake end could always be metal.

[Razer440]

I have drilled and slotted rotors on my car. Granted the ones on there warped easily, but they came from Ebay.Not sure of the quality of the rotors. But with a good rotor for daily driving they shouldn't. I love them even though they are warped, and next spring I will be replacing them with another set of Drilled and slotted rotors and good pads. My thought is its better to have and not need them, then to need them and not have them. I don't care what anyone else says about them. In the end if you want to spend the extra money on them you have that right. Just my thought.

[stealthee]

So you're saying that you don't care that facts are facts and that wasting money on drilled rotors that are just for looks is ok?

[MaxClass]

FYI: I have a copy of Consumer Reports from 1991 that did a review on the "Dodge Stealth RT/Twin". The review was rave overall and one of the best points was that [totally stock] it set a new record with them for the shortest stopping distance ever recorded from 60 to 0 at 122 feet. That has since been beaten but not by much and that's in a car that weighs in, with a driver and some fuel, at 4000 pounds.

Bottom Line: The stock brakes on these cars can stop on a dime and give you nine cents change. Then the little putty knife pups up out of the dash and scrapes you off the windshield. No slots, no holes. If it's a daily driver stock [TT] disks and rotors will give you all you can use.

Anything else will be a waste of you money which I'm sure you can find something else you would like your car to have with the extra cash.

[R/T93]

My DBA 4000's and Carbotech ax6's have more bite than any stock setup can provide. XP 10's or 12's with R compounds I am sure this car's braking performance with a stock weight/caliper car is probably in the high 90 foot range.

[DocWalt]

The problem with the stock brakes is that they overheat like crazy when you push them. I faded stock pads without even trying. They'll give you that one stop no issue. A lot of people don't think about it, but most performance brakes are limited by the tires.

Of course, the pads I have now pretty much suck too :(

[stealthee]

Brakes stop the axles, but tires stop the car.

[GTOJOE]

I warped my stock rotors after a 100km/h to 10km/h in a a VERY short time hahaha. Came around a caorned going down a very steep hill and found a truck doing about 10km/h. The brakes did their job very well on stock rotors. However they can only do it once then they need replacing. I wanted to replace them with DBA slotted but could not find any in the whole city and I needed them that day. Only one instock at the time was the slotted and cross drilled. They are so much better than the stock rotors. Also being DBA they have the kangaroo paw design heat dispersal method so they run a lot cooler. However I do check them for cracking. So far so good.

http://i299.photobucket.com/albums/mm289/1STGENGTO/DBA213X.jpg

[R/T93]

My DBA 4000's have begun to crack here
http://i28.photobucket.com/albums/c201/Ultor2/VR4/Brakes/brakes.jpg

The red is the crack. Its very thin, but visible if you crouch down by the wheel and look. Each inner long slot has the crack, both sides.
I am harder on my brakes than 95% of the members here, though. These rotors would be an excellent street rotor but I am still searching for a good rotor for racing.

[GTOJOE]

DBA make a racing rotor but not for the 3S :(

[R/T93]

If they had the DBA 5000's I would try them out.

I may have a lead on SCE's WIDE rotors though :) that may be the key to my overheating the rotors!! Nascar rotors can handle some abuse.

[Irocurstang]

My experience with drilled/slotted rotors is they warp easier and are less reliable. Its better to stay with a standard rotor and good pad.

[bluemax_1]

Stay tuned folks. If you want real information on brake systems and brake tech, I'll post when I have some time.


Max

[Polygon]

Another misconception is warping. There's only one way you can warp a rotor, and that due to uneven torque distribution across the HUB. Otherwise, they will crack before they warp. What you're experiencing is a build up of pad material on the rotor which happens when you overheat the brakes.


Stay tuned folks. If you want real information on brake systems and brake tech, I'll post when I have some time.


Max

I can't wait to see that!

[ChargerX3]

Another misconception is warping. There's only one way you can warp a rotor, and that due to uneven torque distribution across the HUB. Otherwise, they will crack before they warp. What you're experiencing is a build up of pad material on the rotor which happens when you overheat the brakes.



I can't wait to see that!

True...btw how did i know that i was going to find you on here?

[Polygon]

True...btw how did i know that i was going to find you on here?

Hahaha! There's not many things I feel I know a GOOD deal about on cars and brakes are one of them.

[a2j]

so most of the performance cars that have slotted/drilled rotors are just for show? I mean, there is gotta be some other reason than that. also, about professional racing... they have rules! like no holes, no carbon, limited rotor size, etc... everybody seems to have their own "right" opinion about it, I guess the only way to find out is to run different rotors on the track.

[DocWalt]

Drilled rotors are pointless.

[Jimvr4]

Stay tuned folks. If you want real information on brake systems and brake tech, I'll post when I have some time.


Max

Subscribed :D

[stealthee]

so most of the performance cars that have slotted/drilled rotors are just for show? I mean, there is gotta be some other reason than that. also, about professional racing... they have rules! like no holes, no carbon, limited rotor size, etc... everybody seems to have their own "right" opinion about it, I guess the only way to find out is to run different rotors on the track.

Its not an opinion. Its facts and physics.

[Polygon]

Its not an opinion. Its facts and physics.

Exactly.

The reason that exotics have drilled rotors as an option is because they sell. That's the only reason. Once again, it has already been posted that cross-drilled rotors were originally used in professional racing 40 plus years ago because of brake pad out gassing. Pads don't out gas anymore thus they don't use them anymore. It has nothing to do with rules. There's no reason for a sanctioning body to make a rule about something that is irrelevant. Rules or not, they wouldn't be using them. Also, stop including slotting with cross-drilled. Slotting has proven effectiveness.

[hotGTO]

I don't disagree that drilled on a street car is more show and not performance, but it is true and has been pointed out that there are valid reasons for using drilled in specific applications. Usually when the weight of the rotor is very important, and when they do not need to tax the rotor with constant high heat circumstances... Also, as for heat dissipation, just to argue the physics of it, if drilled was used to dissipate that thin layer of gasses that apparently isn't even a problem any more, then they should dissipate hot "air" in the same manner... The interesting part is the "more surface area" debate which does depend on the thickness of the rotor as pointed out, but they would have to be REALLY thin for the holes to decrease surface area. But a GOOD point!

[stealthee]

I don't disagree that drilled on a street car is more show and not performance, but it is true and has been pointed out that there are valid reasons for using drilled in specific applications. Usually when the weight of the rotor is very important, and when they do not need to tax the rotor with constant high heat circumstances... Also, as for heat dissipation, just to argue the physics of it, if drilled was used to dissipate that thin layer of gasses that apparently isn't even a problem any more, then they should dissipate hot "air" in the same manner... The interesting part is the "more surface area" debate which does depend on the thickness of the rotor as pointed out, but they would have to be REALLY thin for the holes to decrease surface area. But a GOOD point!

The point of a rotor is to stop the tires, which stops the car. When a rotor modification adds no performance increase, ie no help in stopping, then its a gimmick, plain and simple.

[hotGTO]

The point of a rotor is to stop the tires, which stops the car. When a rotor modification adds no performance increase, ie no help in stopping, then its a gimmick, plain and simple.

Very true... Is there a study where drilled rotors were put side by side in a test against smooth rotors and the drilled rotors were worse?

[stealthee]

Again its simple physics as to why it doesn't help. And if they did, they'd be used in racing classes everywhere. They are not.

[GTO Assassin]

Again its simple physics as to why it doesn't help. And if they did, they'd be used in racing classes everywhere. They are not.

While I would personally never get cross drilled rotors or recommend them, I really struggle with the "only for show" theory, and yes, I said theory. While I always read Max's posts and believe them 100% as he knows his stuff, I keep seeing race cars here in Oz and overseas using CD rotors. We have Porsche's here that use them racing, amongst other cars. As was mentioned, the new GT-R comes with them standard. (I think) If it's just for show, why didn't those cars just use neons? Or maybe some fluffy dice round the mirror? For show? Come on people, I'm just not buying it.

Scotty

[stealthee]

Its been noted MANY times that cross drilling was used years ago because of out gassing. Thats the only benefit they offered. Pads don't outgas anymore, so cross drilling is NOT needed. Just because cars come with something, doesn't mean its effective. People pay for looks.

[GTO Assassin]

There are other ways you can have better looks Brian. That's my point. I'm not saying you're wrong or that CD rotors are in fact missunderstood or work. Just that I'm confused over the whole 'just for looks' argument.

Scotty

[stealthee]

People are suckers for things that "look cool" and think makes the car better.

[GTO Assassin]

If it comes on a Honda, then yeah, silly suckers. But AGAIN, these rotors are being put on high priced exotics, street cars AND race cars where the owners/drivers aren't stupid.

Scotty

[Polygon]

To say those owners/drivers aren't stupid, well, I don't know about that. I just want to know what they know that the engineers that work on F1 cars missed? I know plenty of people that own personal race cars and drive them that don't know much, if anything about how a car really works. I'm just saying. As for high end exotics. Why not just use some neons? Because, that would look tacky. Cross-drilling doesn't look tacky. Also, most people buying a high end exotic don't necessarily have a great understanding about brakes.

StopTech will even tell you that CD is for looks and should only be used on the street and you can write what they don't know about brakes on the head of a pin.

[DV8]

I bought a full set of porterfield kevlar pads and slotted/dimpled rotors for my 94Vr4......they stop on a dime, look great, don't dust, and have developed no cracks (yet). They were purchased from another member who wrecked his car before he had a chance to install them. What a deal!...$300 for SS lines and the above new/never installed (from Supercar Engineering). I love them.


The wider slots on these rear rotors actually draw cool air across the pad surface keeping pads and rotors cooler. These rotors also expel dust, dirt and hot gases better than fine slots which eventually fill with rust and scale. The blind drilled holes break down surface gases when braking from speed but do not weaken the rotor cross section as can happen with through drilling, thereby lessening the chance of rotors cracking over time and heavy use.

Extra benefits of sport rotors are not often spoken about but are very worthwhile. This is the effect the slots have on maintaining a flat smooth pad surface during the pads wear life. The slots encourage the pads to wear with a more flat pattern and the "Ribbing" common with non slotted rotors does not appear. This removes the "Record groove" effect of pads on plain rotors, particularly around the outer edge and helps pads maintain better contact area with the rotor through their life.

[hotGTO]

I would like to see the proof in a side by side test that shows that cross drilled rotors are no better than stock rotors at cooling and stopping power with fade tests and wet dry tests and temperature tests... because saying "Its simple physics" is no real answer nor does it make a claim true. It has been noted that cross drilled rotors are better at heat dissipation many times also, but that does not make that true either. Where are the tests being used to determine that drilled rotors are just for show? Because someone somewhere had to prove that they were not better than stock for everyone to believe it, so where is that proof? Because the physics are not rally that simple or else companies would not spend millions to develop new technologies.

[Polygon]

I would like to see the proof in a side by side test that shows that cross drilled rotors are no better than stock rotors at cooling and stopping power with fade tests and wet dry tests and temperature tests... because saying "Its simple physics" is no real answer nor does it make a claim true. It has been noted that cross drilled rotors are better at heat dissipation many times also, but that does not make that true either. Where are the tests being used to determine that drilled rotors are just for show? Because someone somewhere had to prove that they were not better than stock for everyone to believe it, so where is that proof? Because the physics are not rally that simple or else companies would not spend millions to develop new technologies.

You know, I would love it if someone would do a REAL scientific side by side test between the two as well. On the other hand, I find the fact that you're writing off proven physics as simply absurd. We have explained this to you more than once and it's getting old. Physics are proven, we've explained the physics of why they don't work as well to you, yet physics just seem to be for suckers. Yes, someone said that CD rotors dissipate heat better though increased surface area. This is proven physics as well. However, everyone agreed that the gain would be VERY marginal. That is the ONLY gain I can see from CD rotors and it's far outweighed by the negatives. Lastly, we told you that CD rotor were developed by race teams some 40+ years back because of out gassing which was caused by the brake pads. The holes meant that the gas had somewhere to go rather that building up between the pad and the rotor. They had a use, that's why race teams developed them. PADS DON'T OUT GAS ANYMORE SO CD ROTORS HAVE NO MORE USE THUS RACE TEAMS STOPPED USING THEM QUITE A WHILE BACK.

I just don't understand how you're still arguing about this. There's a reason that top end race teams don't use them. It isn't rules, it's because there's no point and they would rather avoid a rotor exploding when they're trying to stop. I think they know a hell of a lot more about this than any of us. Top top it off, I'll say it one more time, and I doubt anyone will refute that StopTech is one of the leaders in brake engineering. Even they say that they will suggest CD rotor for street use ONLY as they can't stand up to track abuse.

I suggest you read through this thread again. It's all laid out for you in the simplest of explanations. Physics are proven, your opinion is not. I would love to see a test to as it would prevent asinine arguments like this all together, but it's really not needed for anyone that understands simple physics. If the laws of physics just aren't good enough for you, well then I'm sorry.

[hotGTO]

You know, I would love it if someone would do a REAL scientific side by side test between the two as well. On the other hand, I find the fact that you're writing off proven physics as simply absurd. We have explained this to you more than once and it's getting old. Physics are proven, we've explained the physics of why they don't work as well to you, yet physics just seem to be for suckers. Yes, someone said that CD rotors dissipate heat better though increased surface area. This is proven physics as well. However, everyone agreed that the gain would be VERY marginal. That is the ONLY gain I can see from CD rotors and it's far outweighed by the negatives. Lastly, we told you that CD rotor were developed by race teams some 40+ years back because of out gassing which was caused by the brake pads. The holes meant that the gas had somewhere to go rather that building up between the pad and the rotor. They had a use, that's why race teams developed them. PADS DON'T OUT GAS ANYMORE SO CD ROTORS HAVE NO MORE USE THUS RACE TEAMS STOPPED USING THEM QUITE A WHILE BACK.

I just don't understand how you're still arguing about this. There's a reason that top end race teams don't use them. It isn't rules, it's because there's no point and they would rather avoid a rotor exploding when they're trying to stop. I think they know a hell of a lot more about this than any of us. Top top it off, I'll say it one more time, and I doubt anyone will refute that StopTech is one of the leaders in brake engineering. Even they say that they will suggest CD rotor for street use ONLY as they can't stand up to track abuse.

I suggest you read through this thread again. It's all laid out for you in the simplest of explanations. Physics are proven, your opinion is not. I would love to see a test to as it would prevent asinine arguments like this all together, but it's really not needed for anyone that understands simple physics. If the laws of physics just aren't good enough for you, well then I'm sorry.

Why are you attacking me for wanting proof? Why are you accusing me of having an opinion when I never even offered an opinion? When have I said that "I believe drilled rotors are better than stock rotors" ? I suggest YOU read this entire thread! A lot of people are saying it is simple physics, but no one has shown any proof! And I am not talking about F1 or any other racing application, I am talking about comparing stock to CD... Sure racers have come up with better technology for the track than drilled, but that does not automatically mean drilled is not still an upgrade from stock. And I'm not saying it is my opinion that they are an upgrade either, but I still want to see where it has been proven that they are no longer better than stock, because for quite a while EVERYONE including YOU thought they were better than stock because racers WERE using them. Now just because racers have moved on to newer technology a lot of people are saying drilled is pointless or else racers would still use them, and that is a load of unproven bull. If they were pointless then racers would have NEVER used them, and if they are less effective now, where are the tests proving they are less effective? Don't lambast me because I am asking a question that you can't answer!

[GTOJOE]

Personally I think my brakes feel better with them compared to the stock rotors. I didn't want CD but it was all that was available on the day. But i'm happy with them. Also to the ppl saying rotors don't warp that's utter BS. I have personally seen many times warped rotors on a brake lathe. They are warped! I have driven cars with warped rotors. Replaced or machined the rotors while keeping the pads and they are perfect. Sure pads may be the cause of some issues but it's ignorant to state they don't warp.

[i3igpete]

http://papers.sae.org/2006-01-0691/
The Effect of Rotor Crossdrilling on Brake Performance
Author(s):
David Antanaitis - General Motors Corp.
Anthony Rifici - General Motors Corp.



For those that are interested in upgrading from a stock rotor to either drilled or slotted, read this from an engineer's stand point. I helped me make my decision to just get drilled rotors on all four corners. Thank..

There are many claims as to the benefits of drilled vs slotted rotors on stopping power. This guide is intended to provide some facts about drilled and slotted rotors. As a member of the SAE (Society of Automotive Engineers), I was pleased to see a paper "The Effect of Rotor Crossdrilling on Brake Performance" by two GM engineers published in 2006. They examined three vehicle platforms with cross-drilled rotors vs standard rotors to measure convection cooling capability, fade characteristics, wet braking, pedal feel and lining wear. The result is summarized as follows:

For the sports sedan, the coefficient of friction was 21% higher for drilled rotors than standard front rotors at 340F and higher using 15 brake snubs at 62mph. The track simulated 124 mph fade test showed 37% better brake output for drilled rotors. The drilled rotor brake temperature was about 150 degrees cooler.
For the performance car, the coefficient of friction was significantly higher for drilled rotors especially at high temperature.
Wet braking at high pedal pressure was the same for drilled or standard rotors. Wet braking is not significantly improved by drilled rotors.
Pedal force was much more consistent with drilled rotors over the brake temperature range. That is, to stop at the same deceleration rate, the driver does not need to modulate pedal pressure based on different brake temperatures. This reduces driver fatigue and improves brake response.
The authors also reported that drilled rotors prevent pad resin glazing on the rotor. So we now have solid evidence that drilled rotors have benefits over standard rotors. However, I have not found any published paper to show how slots affect brake output. So I reviewed inertial dynamometer tests using ISO NWI 26867 from Link Testing in Detroit with slotted rotors vs standard rotors. The results showed no significant difference in the coefficient of friction during the fade sections, hot stop section or pedal sensitivity portion of the test. My hypothesis is that slotted rotors do not contribute to rotor cooling whereas drilled rotors improve convection heat transfer to cool rotors and reduce brake fade. I should also point out that the pad lining wear for the slotted rotor was very severe during the test, i.e. the pad was chewed up over 20% more than the lining with stock rotors. While I believe that slots will help remove gas and debri from under the pad, I am not sure that this has a significant effect on brake torque for normal street driving. Perhaps the effect of slotted rotors is more significant on the race track, and conversely, I believe that drilled rotors are better for street and highway driving. For most drivers, I recommend drilled rotors over slotted rotors, and this conclusion is supported by the fact that Corvette, Ford GT, Porsche, Mercedes and BMW come with OEM drilled rotors.

[DV8]

http://www.stoptech.com/tech_info/tech_white_papers.shtml

[i3igpete]

but conversely...



How is the coefficient of friction of a HOLE greater then solid sides ?

BUT what they did not say or show is REAL APPLICATIONS.
here are a few pics from minimal use on tracks

http://img.photobucket.com/albums/v172/AUNEGL/CrackedRotor.jpg

http://img.photobucket.com/albums/v172/AUNEGL/Cracked_DBA_Rotors001.jpg

http://img.photobucket.com/albums/v172/AUNEGL/Brakes/Rotor_BigCrack.jpg

http://img.photobucket.com/albums/v172/AUNEGL/Brakes/rotor-DScracks-2.jpg

and less the one hour use. TWO twenty min session
http://img.photobucket.com/albums/v172/AUNEGL/Brakes/rotor_C6Z_17_laps.jpg

and ONE twenty min session

http://img.photobucket.com/albums/v172/AUNEGL/NASA/PorscheRotor.jpg

Yup those drilled, milled or cast in holes work great. :rolleyes:

Drill and slotted rotors are 40 year old technology to release or out gas asbestos brake pad gasses. Guess what? asbestos has not been used for brake pads in 40 years, so no need for holes.

Why do manufactures keep putting holes in rotors? because the customer wants them. PERIOD. No functional use.

That research was flawed.

[hotGTO]

http://papers.sae.org/2006-01-0691/
The Effect of Rotor Crossdrilling on Brake Performance
Author(s):
David Antanaitis - General Motors Corp.
Anthony Rifici - General Motors Corp.
That's just a link where to buy the paper, but it doesn't really answer the question unless you buy the paper... Does anyone have a free version of that report?

[i3igpete]

That's just a link where to buy the paper, but it doesn't really answer the question unless you buy the paper... Does anyone have a free version of that report?


i copy pasted the synopsis for you, and took time to highlight the important bits. :glare:

[Polygon]

Why are you attacking me for wanting proof?

I'm not. That's the only part of your post that didn't annoy me.


Why are you accusing me of having an opinion when I never even offered an opinion? When have I said that "I believe drilled rotors are better than stock rotors" ?

I hate to break it to you, but that's an opinion.


I suggest YOU read this entire thread! A lot of people are saying it is simple physics, but no one has shown any proof!

As I have said time and time again in this thread, the physics are the proof. Nobody has done a proper scientific test between the two, so the laws of physics are the only proof we have which are good enough for me. That is the reason I attacked you. The laws of physics aren't good enough for you. When a gas expands it cools, that's simple physics, but you won't believe it unless I show you some proof. I've even showed that the people that engineer these brakes don't recommend them either, but what do they know?

It's pretty absurd.


And I am not talking about F1 or any other racing application, I am talking about comparing stock to CD... Sure racers have come up with better technology for the track than drilled, but that does not automatically mean drilled is not still an upgrade from stock. And I'm not saying it is my opinion that they are an upgrade either, but I still want to see where it has been proven that they are no longer better than stock, because for quite a while EVERYONE including YOU thought they were better than stock because racers WERE using them. Now just because racers have moved on to newer technology a lot of people are saying drilled is pointless or else racers would still use them, and that is a load of unproven bull. If they were pointless then racers would have NEVER used them, and if they are less effective now, where are the tests proving they are less effective? Don't lambast me because I am asking a question that you can't answer!

1. Well, stock to CD, that's pretty general. If you wanted to do a real scientific test between the two here's what you would have to do.

You need to start with a control.
Flush the brake fluid.
Change the brake pads.
Replace the rotors with OEM sized blanks.
Run your stopping tests and checking temperatures.
Once you've completed those start over.
Flush the brake fluid again with the exact same fluid.
Change the pads again with the exact same pads.
Change the rotors the the CD. They need to be the EXACT same rotors, just cross-drilled. Same size, same metallurgical properties, everything. Just the addition of cross-drilling.
Run the tests again.


If you move UP in size or get better quality rotors that are CD, yes they will probably stop better and resist fade better than stock rotors. That's why you need to test with the EXACT same rotors.

2. This is getting ridiculous. You need to stop using the word stock, they're called blanks. We've told you that racing teams developed them to fix a problem a long time ago that no longer exists. It isn't a problem that exists anymore for the street or the track. They didn't FIND or DEVELOP a better or newer technology. They simply went back to using blanks.

3. We have told you that out gassing was a problem created by brake pads back then. The holes gave the gas somewhere to go. The build up of gas between the rotors and the pads caused VERY poor braking performance. That is why they developed them. PADS DON'T OUT GAS ANYMORE, THEY HAVEN'T FOR DECADES. That is why racing teams went back to using blanks. How many time do we have to say it?

I'm lamb basting you because these are some of the most ignorant posts I've seen. The information is there, but you refuse to believe the laws of physics, brake engineers, racing engineers. You want a test that shows what is proven science. That's fine, I would love one to. It just irritates me that the other ting hold no merit to you even though most of the rest of the population understands these concepts. Add that fact that you keep refuting a point when the information is right there meaning I have to repeat myself. I mostly referring to the fact that racing doesn't use them anymore.

I'm done with this thread. I know that cross-drilling a rotor reduces it's contact patch with the pad, reduces it efficiency, and reduces it's strength. The laws of physics taught me that those three things means it's a worse rotor that the exact same rotor that's a blank and that it won't stop as well.

I'm sure that will never be enough for you and I doubt anyone is really going to do a proper scientific test of this.

/rant

[DV8]

David Antanaitis (http://www.sae.org/servlets/product?PROD_TYP=PAPER&ACN=76798383408&AUTHOR_NAME=David+Antanaitis&PLA_SW=YES)
Patent application title: Disk Brake Friction Surfaces with Tunable Indent Patterns for Minimizing Brake Pad Radial Taper Wear

to skip all the technical engineering....goto "Examples" (~80% down the page)
http://www.faqs.org/patents/app/20090266653

[hotGTO]

i copy pasted the synopsis for you, and took time to highlight the important bits. :glare:

Hey, thank you! that was very cool of you to do so!

[hotGTO]

I'm not. That's the only part of your post that didn't annoy me.



I hate to break it to you, but that's an opinion.



As I have said time and time again in this thread, the physics are the proof. Nobody has done a proper scientific test between the two, so the laws of physics are the only proof we have which are good enough for me. That is the reason I attacked you. The laws of physics aren't good enough for you. When a gas expands it cools, that's simple physics, but you won't believe it unless I show you some proof. I've even showed that the people that engineer these brakes don't recommend them either, but what do they know?

It's pretty absurd.



1. Well, stock to CD, that's pretty general. If you wanted to do a real scientific test between the two here's what you would have to do.

You need to start with a control.
Flush the brake fluid.
Change the brake pads.
Replace the rotors with OEM sized blanks.
Run your stopping tests and checking temperatures.
Once you've completed those start over.
Flush the brake fluid again with the exact same fluid.
Change the pads again with the exact same pads.
Change the rotors the the CD. They need to be the EXACT same rotors, just cross-drilled. Same size, same metallurgical properties, everything. Just the addition of cross-drilling.
Run the tests again.


If you move UP in size or get better quality rotors that are CD, yes they will probably stop better and resist fade better than stock rotors. That's why you need to test with the EXACT same rotors.

2. This is getting ridiculous. You need to stop using the word stock, they're called blanks. We've told you that racing teams developed them to fix a problem a long time ago that no longer exists. It isn't a problem that exists anymore for the street or the track. They didn't FIND or DEVELOP a better or newer technology. They simply went back to using blanks.

3. We have told you that out gassing was a problem created by brake pads back then. The holes gave the gas somewhere to go. The build up of gas between the rotors and the pads caused VERY poor braking performance. That is why they developed them. PADS DON'T OUT GAS ANYMORE, THEY HAVEN'T FOR DECADES. That is why racing teams went back to using blanks. How many time do we have to say it?

I'm lamb basting you because these are some of the most ignorant posts I've seen. The information is there, but you refuse to believe the laws of physics, brake engineers, racing engineers. You want a test that shows what is proven science. That's fine, I would love one to. It just irritates me that the other ting hold no merit to you even though most of the rest of the population understands these concepts. Add that fact that you keep refuting a point when the information is right there meaning I have to repeat myself. I mostly referring to the fact that racing doesn't use them anymore.

I'm done with this thread. I know that cross-drilling a rotor reduces it's contact patch with the pad, reduces it efficiency, and reduces it's strength. The laws of physics taught me that those three things means it's a worse rotor that the exact same rotor that's a blank and that it won't stop as well.

I'm sure that will never be enough for you and I doubt anyone is really going to do a proper scientific test of this.

/rant

You can NOT read! I wrote: "When have I said that""I believe drilled rotors are better than stock rotors" ? With a QUESTION MARK!

Edit: It looks like real testing of drilled brake rotors as compared to stock rotors blows your "everyone knows physics" out of the water!

[DV8]

Ain't they pretty? slotted and dimpled......FTW

[i3igpete]

I'm sure that will never be enough for you and I doubt anyone is really going to do a proper scientific test of this.
/rant

Please see my posted link and synopsis. I was surprised by the results, as I'm sure the engineers were. However, the durability problems should not be a surprise at all.

[GordonRamsey]

Please see my posted link and synopsis. I was surprised by the results, as I'm sure the engineers were. However, the durability problems should not be a surprise at all.

I was in a base model GT and it had stock size drilled rotors and upgraded pads, and it just about through my face off. but then again, I wonder how long it would take to crack them.

[hotGTO]

Are the high quality rotors really failing under normal street use? They might stand a good chance of surviving normal street usage since they are included as a factory option on some models. Manufacturers don't like to pay high dollar settlements so they don't usually sell parts that are known for failure as a factory installed option... And they might be listed as only an appearance upgrade because they are only for the street and not mistaken for a race application to be beaten until failure...

[bluemax_1]

LOL, Pete beat me to the punch as I hadn't had time to really post yet. I posted the results of that SAE paper on the 'other' forum back in '07 but I guess not too many folks read it, but Pete summed it up perfectly:

- Crossdrilled rotors actually DO reduce brake temps AND increase brake torque.
- It's not a good idea to use them on track because the holes create stress risers that cause the cracking in the pics Pete posted
- I personally wouldn't use them on any car driven hard even if not taken to the track (etc. mountain runs).
- Crossdrilled are best for street driven cars that occasionally see a little 'spirited' driving

After reading the interesting results of the GM study, I was curious so I did a little more research. One of the key impressions is that the holes didn't make that much difference in radiant area and this is true, but as the compiler of the SAE paper mentions, it's the convective cooling benefits that come into play.

In the old days, when they first started crossdrilling rotors due to pads outgassing, there were a lot of non-vaned drilled rotors. The holes were mainly for the outgassing and didn't affect convective (or radiant) cooling much because the holes were straight through the flat plane of the rotor, and as folks can easily see, the holes are perpendicular to the direction of travel (as the rotor is spinning) and there's not much airflow through them at all. With vaned rotors though, there is a lot of airflow through the vanes because they act in a manner similar to the impellers in turbos and hairdryers. They suck air in at the center/hub and the centrifugal force forces the air outwards (alright, no smartass comments about centripetal vs non-existent centrifugal forces). That means a lot of airflow through the vanes, and because of the big differential between airflow on the inside of the holes (in the vanes) vs the outside faces of the rotors, there actually is a substantial amount of airflow through those crossdrilled holes causing the resultant improvement in cooling.

They also increase brake torque through mechanical means. Although brake pads feel hard to the touch, at the pressures (and temperatures) seen under braking, they are actually malleable. They conform to the surface of the rotor. The holes from drilling (or dimples) and to some extent slots, cause indentations in the surface plane of the rotor and the malleable surface of the pads slightly bows into those depressions. The trailing edge of the depressions increases 'bite' into the pads thereby increasing brake torque. That is also why they wear pads faster. It really does act something like a cheese grater. The hotter your pads get, the more the surface will be affected, but the continual wiping of the surface prevents the pads from glazing over which is the main reason some race teams use slotted rotors (while others stick to blanks). Although modern pads don't outgas the way old pads used to, they can still glaze over.

The reason normally slotted rotors don't cause as significant an increase in brake torque as crossdrilled rotors do is due to the fact that drilled rotors are generally drilled with a pattern that has enough holes that at any given moment, there are numerous edges under the pads to create that increased bite. If you look at the regular slotting pattern in most slotted rotors (usually 6-8 long slots) at any given time, there is very little 'edge' under the pad to create the added bite. This is why some race teams (and brake companies like Baer and AP Racing for instance) have developed different slotting patterns like the numerous short slots.

The newer different slot designs (some of which cost more to machine) use many short slots. One of the designs use 3 'rings' of staggered short slots. Each slot is slightly longer than 1/3 the length of a normal 'long' slot. They are staggered in a way that ensures that the edges of the 3 rings of slots very slightly overlap so the entire swept area of the slots is similar to the long slot swept area. At any given moment though, there are many more edges under the pad surface to provide the increased bite, but if the slots are properly machined (in particular, the ends of the slots must be properly radiused), they do not create the stress risers that cause the cracking that drilled rotors do under racing or severe use conditions.

The other odd slotting design that works even better than the '3 rings' slotting is J-hook slotting (a design, I believe developed by AP Racing). The slots are machined to look sort of like the letter 'J'. The J-hook slots increase pad bite as much as (or sometimes more than) crossdrilled rotors (because they have as much or sometimes more total 'edge' under the pad surface for initial bite), but don't cause the cracking under racing.

This is an example of what J-hooks look like
http://www.stillen.com/product.asp?id=STIGTRCVRT&c=BR&year=2009&make=NISSAN&model=GT-R

The only place that I currently know of that 3/S owners 'might' be able to get J-hook pattern rotors for stock 3/S brakes is KVR. Now I won't lie, KVR rotors are NOT cheap, but I've used them in the past (not J-hooks though :( ) and they are, IMHO, worth the money. In fact, after moving to 355 Stoptechs in front, I STILL use slotted KVR's in the rear and those puppies are holding up perfectly fine (got them cadmium plated so the centers wouldn't rust).

If Stoptech ever gets around to adopting the J-hook pattern, I'll probably get a track pad set of rotors.

BTW, my slotted Stoptech fronts and slotted KVR rears show ZERO signs of stress cracking even after being run on the track numerous times.


Max

P.S. Forgot to add, aside from cracking issues from serious, severe track use on 'holey' rotors (since it doesn't matter that much whether the holes are drilled or cast), on rotors of a given size, their mass is STILL the mass of the heatsink, and as such, removing the amount of material from lots of holes is still removing mass (and thus thermal capacity) from the heatsink. Thus far, there have been no conclusive tests that have demonstrated whether the improved cooling from the holes offsets the reduced thermal capacity under track conditions (keep in mind that we're talking about rotors of the same dimensions. You can of course, use bigger holey rotors to maintain the mass of the heatsink). IIRC, the SAE paper actually used slightly different diameters of rotors in their tests (can't recall why. Might have been due to availability), but that still doesn't change the fact that they will crack eventually under severe use.

P.P.S. If slotted rotors are chosen, AVOID end-slotted rotors (where the slots reach the ends). Although some members have posted pics of rotors that crack with slots that don't reach the ends (the slot ends were probably not radiused properly), end-slotted rotors WILL crack if used hard.

P.P.P.S. As with motor oil, if you drive like a grandmother in a Buick, use whatever you like. If you don't push the car hard, it won't make much of a difference.

[Jimvr4]

Please see my posted link and synopsis. I was surprised by the results, as I'm sure the engineers were. However, the durability problems should not be a surprise at all.


LOL, Pete beat me to the punch as I hadn't had time to really post yet. I posted the results of that SAE paper on the 'other' forum back in '07 but I guess not too many folks read it, but Pete summed it up perfectly:


Max

Been waiting for the voices of reason on this thread. Thanks to both of you for posting :D

I used to track my 91 VR4 years ago. I started with stock brakes which faded badly after only a couple of laps. I boiled the fluid and glazed the rotors. Next trip to the track I had upgraded fluid, carbon kevlar pads, and drilled rotors. The new setup was capable enough for the cornering speeds I was comfortable with. When I got my Spyder I experienced brake problems again with stock rotors and compounded by the increased weight. I switched to slotted / dimpled rotors 7 years ago and they're still holding up. Of course I haven't tracked the Spyder so it doesn't see the level of temperatures that would put the rotors at risk. No cracks or visible stresses after 7 years (36k miles) :p

http://jns.jimnshar.com/0f280a90.jpg

[Polygon]

You can NOT read! I wrote: "When have I said that""I believe drilled rotors are better than stock rotors" ? With a QUESTION MARK!

Edit: It looks like real testing of drilled brake rotors as compared to stock rotors blows your "everyone knows physics" out of the water!


Please see my posted link and synopsis. I was surprised by the results, as I'm sure the engineers were. However, the durability problems should not be a surprise at all.

I have to question that. I kind of have to take his word for it. He doesn't show his testing parameters. There's no talk of a control. What rotors were used, were they identical save for the cross-drilling? Did he use a fresh set of brake pads each time and were they the same. Was this on the same car, or perhaps testing rig? Did he also change the fluid after each test? Like I said, I still have yet to see a PROPER scientific test that proves physics wrong. So, no, that doesn't blow physics out of the water.


Are the high quality rotors really failing under normal street use? They might stand a good chance of surviving normal street usage since they are included as a factory option on some models. Manufacturers don't like to pay high dollar settlements so they don't usually sell parts that are known for failure as a factory installed option... And they might be listed as only an appearance upgrade because they are only for the street and not mistaken for a race application to be beaten until failure...

No, those failures should not be an issue with street driving. At least they shouldn't as long as people don't drive like an asshole everywhere. Small cracks might start show up but I highly doubt you'd get actual failure from street driving on GOOD CD rotors. The cheap eBay crap, well, those could do anything but simply because they're cheap.

[mb7050]

good posts .

real brakes / discs

1st
http://images.motortrend.com/photo_gallery/112_0702_10z+f1_driving_contest+brakes.jpg

J-hook pattern rotors been used in rally cars for years its proven to be the best desing so far .

[bluemax_1]

Polygon,

yes, it hurts to have your theories smack you in the face (I'm sorry, even when I didn't have time to post yet, there was a bit of perverse pleasure in watching the arguments and noting the holes folks were digging for themselves). But SERIOUSLY? If you want to look at the SCIENTIFIC test results, why don't you pay for the SAE paper yourself like Pete and I obviously did. It's not as if it's THAT astronomically expensive (something like $14.95?).

I only posted my findings from it on the 'other' forum because I didn't want to reproduce a copyrighted article.


Max

[bluemax_1]

BTW, bear in mind that F1 carbon brakes are a whole different ballgame. Those puppies were designed for several reasons, one being that F1 rules dictate that brake rotors can't be more than 315mm in diameter. Carbon brakes can also withstand temps that cast iron rotors would fail at. In addition, those vaned holes are force fed. See that carbon shroud? That thing forces air at the rotors. Another thing is that the carbon rotors can withstand extreme heat cycling better than cast iron rotors can.

Did you guys know that too much cooling for a cast iron rotor is a bad thing? All brake systems work best within an optimal temp range (which is why track only pads shouldn't be used on the street, because they'll never get up to proper operating temps without driving in a dangerous an illegal manner on public streets). In professional racing, brake cooling ducts are used to direct air at the brake systems to ensure they don't overheat. With cast iron rotor brake systems though, teams tend to adjust the amount of ducting depending on the track and conditions. They reduce the ducted airflow on less brake intensive track because they don't want too much air to cool down the rotors too much, for instance, tracks where there are less intense braking sections followed by long straightaways. They don't want too much ducting because it could potentially cool the brakes too much before the end of the straights. The reason is not that the brakes have cooled below minimum operating temps (one hard braking event easily takes care of that), the reason is because it will cause too much extreme thermal cycling in the brake rotors. When there are HUGE temperature swings between hot rotors when the brakes are applied and cooled rotors as the car is flying round the track, the temp variations cause a lot of thermal stress that results in lots of cracks, so they reduce brake ducting while testing the setup at the track to minimize the temp variation.

True F1 type carbon brakes can be had.... for somewhere around $30,000 - $50,000? Then of course, there are the performance street carbon composite rotors (like the options for Porsches and Vettes) which can be had for ONLY ~ $12k - $20k. I've been waiting for those guys at ATS/ACROSS to produce vented carbon rotors that can be used on a 3/S ever since I saw the carbon brake prototype years ago.


Max

[Polygon]

Polygon,

yes, it hurts to have your theories smack you in the face (I'm sorry, even when I didn't have time to post yet, there was a bit of perverse pleasure in watching the arguments and noting the holes folks were digging for themselves). But SERIOUSLY? If you want to look at the SCIENTIFIC test results, why don't you pay for the SAE paper yourself like Pete and I obviously did. It's not as if it's THAT astronomically expensive (something like $14.95?).

I only posted my findings from it on the 'other' forum because I didn't want to reproduce a copyrighted article.


Max

Well, will you at least tell me if the article discloses all of the testing that led them to their results? If not, then it's a waste of money as it's results would be irrelevant. If they do then I have no problem paying to look at the article. However, I'm not butt hurt in any way as I have yet to be proven wrong. All I have are people posting information from an article but no facts to back them up. I have no problem admitting I'm wrong if that's the case. But I will not do so until I've been proven wrong.

[i3igpete]

yes. SAE articles are peer reviewed for content. It is a published in a scientific journal. Shall I go into the SAE review process? I've edited and reviewed several myself.

Typically, after a paper is submitted it gets delegated to a person with a similar background in the industry, this is the section chair. This is so a paper on crash testing procedures isn't handled by someone with a background in lubrication. Then, it gets reviewed by 3-5 other experts with similar background, chosen by the section chair. Here, the reviewers can approve, reject, or send the paper back for editing. It is graded on the depth of past research, innovation, non-commercial integrity, and finally the technical quality of results.

The writers then get one chance to fix any mistakes and resubmit it. If after the second submission a reviewer still dissents with the paper, it will not pass into the SAE yearly journal.

Yes, I have rejected papers and stopped them from getting published.

[Jimvr4]

yes. SAE articles are peer reviewed for content. It is a published in a scientific journal. Shall I go into the SAE review process? I've edited and reviewed several myself.

Typically, after a paper is submitted it gets delegated to a person with a similar background in the industry, this is the section chair. This is so a paper on crash testing procedures isn't handled by someone with a background in lubrication. Then, it gets reviewed by 3-5 other experts with similar background, chosen by the section chair. Here, the reviewers can approve, reject, or send the paper back for editing. It is graded on the depth of past research, innovation, non-commercial integrity, and finally the technical quality of results.

The writers then get one chance to fix any mistakes and resubmit it. If after the second submission a reviewer still dissents with the paper, it will not pass into the SAE yearly journal.

Yes, I have rejected papers and stopped them from getting published.

This particular skill set might come in handy here :p:p

[$$$PIT]

I REALLY didn't mean to cause such a heated discussion when I started this thread. My car is a DD and I don't drive it hard at all. (I'm 48 yrs old and a retired cop.) I simply have an opportunity to upgrade to the VR-4 calipers and liked the looks of the Drilled/Slotted rotors. I have recently competed in a few car shows and thought it would look good. But, didn't want to use them if they were unreliable for everyday street driving.

[GTOJOE]

The general consensis is if it's a street car and not driven too hard. And you buy a good brand they are fine. I have them but I will be watching them closely for cracking.

[hotGTO]

I REALLY didn't mean to cause such a heated discussion when I started this thread. My car is a DD and I don't drive it hard at all. (I'm 48 yrs old and a retired cop.) I simply have an opportunity to upgrade to the VR-4 calipers and liked the looks of the Drilled/Slotted rotors. I have recently competed in a few car shows and thought it would look good. But, didn't want to use them if they were unreliable for everyday street driving.

If that's the case, I think you should go for it. I mean, if you are not going to race it, you will probably never have any issues, and you would get the benefits of whatever better performance they offer on top of the looks. As far as the heated discussion, there are times when we all want to defend our views, it's just human nature, I don't hold grudges when someone doesn't get what I am trying to say even if we exchange a few semi insulting verbal jabs... that just happens to be the only way to joust in an internet forum, as long as there's no name calling, it's nothing to lose sleep about, lol

[GordonRamsey]

I'm glad I stuck around for this discussion. A lot of good information here. I like those J-hook rotors, I never knew they existed.
Does the cadmium plating cover the entire rotor?

[bluemax_1]

I'm glad I stuck around for this discussion. A lot of good information here. I like those J-hook rotors, I never knew they existed.
Does the cadmium plating cover the entire rotor?

It depends on where you get them from. Some places just coat the hats. Others coat the entire thing (the brake pads wear the coating off the swept area of the rotor and the plating prevents/reduces rusting on the hats and the rotor edges and vanes.


Max

[hotGTO]

As I have said time and time again in this thread, the physics are the proof. Nobody has done a proper scientific test between the two*1*, so the laws of physics are the only proof we have which are good enough for me. That is the reason I attacked you. The laws of physics aren't good enough for you. When a gas expands it cools, that's simple physics, but you won't believe it unless I show you some proof. I've even showed that the people that engineer these brakes don't recommend them either, but what do they know?

It's pretty absurd.


2. This is getting ridiculous. You need to stop using the word stock, they're called blanks. *2* We've told you that racing teams developed them to fix a problem a long time ago that no longer exists. It isn't a problem that exists anymore for the street or the track. They didn't FIND or DEVELOP a better or newer technology. They simply went back to using blanks.

I'm lamb basting you because these are some of the most ignorant posts I've seen.*3* The information is there, but you refuse to believe the laws of physics, brake engineers, racing engineers. You want a test that shows what is proven science. That's fine, I would love one to. It just irritates me that the other ting hold no merit to you even though most of the rest of the population understands these concepts. Add that fact that you keep refuting a point when the information is right there meaning I have to repeat myself. I mostly referring to the fact that racing doesn't use them anymore.

I'm done with this thread. I know that cross-drilling a rotor reduces it's contact patch with the pad, reduces it efficiency, and reduces it's strength. The laws of physics taught me that those three things means it's a worse rotor that the exact same rotor that's a blank and that it won't stop as well.*4*

I'm sure that will never be enough for you and I doubt anyone is really going to do a proper scientific test of this.

/rant
Hmmm...

*1* You were proven wrong about that...
*2* I don't HAVE to call stock rotors blanks just to please you!
*3* You called MY posts ignorant? How ironic considering how wrong you are in *4*
*4* I don't even need to say it.. but I will... WRONG AGAIN! :p

And just to be clear, I feel guilty for posting this because I think it overshadows some very good information so I apologize to everyone else, but since you felt so eager to attack me for no reason and try to talk down to me when you were talking out of your ass, and have yet to apologize for the attacks or for calling my posts ignorant (which they absolutely were not) and you still have not admitted you were wrong even after being shown proof, I am allowing myself this guilty pleasure! Thank you for making me laugh so hard when you stated in your last post that you still have not been proven wrong... SO SWEET
:lol:

[Chris GTO TT]

BTW, bear in mind that F1 carbon brakes are a whole different ballgame. Those puppies were designed for several reasons, one being that F1 rules dictate that brake rotors can't be more than 315mm in diameter. Carbon brakes can also withstand temps that cast iron rotors would fail at. In addition, those vaned holes are force fed. See that carbon shroud? That thing forces air at the rotors. Another thing is that the carbon rotors can withstand extreme heat cycling better than cast iron rotors can.

Did you guys know that too much cooling for a cast iron rotor is a bad thing? All brake systems work best within an optimal temp range (which is why track only pads shouldn't be used on the street, because they'll never get up to proper operating temps without driving in a dangerous an illegal manner on public streets). In professional racing, brake cooling ducts are used to direct air at the brake systems to ensure they don't overheat. With cast iron rotor brake systems though, teams tend to adjust the amount of ducting depending on the track and conditions. They reduce the ducted airflow on less brake intensive track because they don't want too much air to cool down the rotors too much, for instance, tracks where there are less intense braking sections followed by long straightaways. They don't want too much ducting because it could potentially cool the brakes too much before the end of the straights. The reason is not that the brakes have cooled below minimum operating temps (one hard braking event easily takes care of that), the reason is because it will cause too much extreme thermal cycling in the brake rotors. When there are HUGE temperature swings between hot rotors when the brakes are applied and cooled rotors as the car is flying round the track, the temp variations cause a lot of thermal stress that results in lots of cracks, so they reduce brake ducting while testing the setup at the track to minimize the temp variation.

True F1 type carbon brakes can be had.... for somewhere around $30,000 - $50,000? Then of course, there are the performance street carbon composite rotors (like the options for Porsches and Vettes) which can be had for ONLY ~ $12k - $20k. I've been waiting for those guys at ATS/ACROSS to produce vented carbon rotors that can be used on a 3/S ever since I saw the carbon brake prototype years ago.


Max

I'd just like to throw in that ALMS cars that run carbon brakes (LMP1, LMP2, GT1) dont used drilled rotors as well. Audi even went to the same style ducting as F1 cars where the rotor isn't visible and air flow is very carefully tuned for the track to keep brakes at their optimal temps.

Also the ALMS cars that run steel rotors (GT2) use slotted, normally j-hook, rotors. These are cars where the rotors are required to last 12, 6, 24, and 10 hours (the longer races). The only race cars i have seen running Drilled rotors on a regular basis are 911 GT3 Cup cars. These are however delivered to customers built by Porsche and are required to run stock components.

[Polygon]

Hmmm...

*1* You were proven wrong about that...
*2* I don't HAVE to call stock rotors blanks just to please you!
*3* You called MY posts ignorant? How ironic considering how wrong you are in *4*
*4* I don't even need to say it.. but I will... WRONG AGAIN! :p

And just to be clear, I feel guilty for posting this because I think it overshadows some very good information so I apologize to everyone else, but since you felt so eager to attack me for no reason and try to talk down to me when you were talking out of your ass, and have yet to apologize for the attacks or for calling my posts ignorant (which they absolutely were not) and you still have not admitted you were wrong even after being shown proof, I am allowing myself this guilty pleasure! Thank you for making me laugh so hard when you stated in your last post that you still have not been proven wrong... SO SWEET
:lol:

:rolleyes:

I highly doubt you've read that article. So, you're probably assuming that it's proven me wrong because it would simply support your opinion. I didn't tell you to call them blanks to appease me, I was trying to help you not sound like an idiot. Just because they're blank faced rotors doesn't make them stock. Your posts are ignorant because I can tell you know next to nothing about braking systems. Pete and Blue do and that's the only reason I'm considering paying to read the article.

So, once again, I haven't been proven wrong yet. I'll save my conclusions for the time being and if I'm wrong I'll admit it. If I still question the articles conclusions, for some reason, I'm highly considering running my own tests with a neutral party.

For the time being I will say this. If you're only going to put them on a street driven car then go ahead and get CD rotors if you want to. If the car will ever see track duty, I'd avoid them like the plague. The cracking issues have always been the most glaring issue with CD rotors. Since the appearance of this article I will rephrase my own conclusions. My theory that CD rotors do not work as well was based on the fact that we would not be talking about a large margin. I would think that it would be a relatively small one.

If I'm wrong I'll admit it. Once I have time to sit down and rear the article, we'll see.

[ChargerX3]

The hate with the drilled rotors is that they crack under extreme use... Probably a lot of ebay crap being sold and breaking under heavy usage causing a growing wave of people to throw them under the bus... Slotteds are even getting dissed a little due to excessive pad wear and cracking under extreme conditions, but I think it is from the growing number of knockoffs and ebay junk that are being marketed to uninformed drivers as "performance" parts when they are in reality only "show" parts!

Edit: Generally always true is "you get what you pay for" if you buy HIGH quality expensive drilled or slotted rotors, you will probably have good results.


http://www.raceshopper.com/tech.shtml#slotted_rotors


Hmmm...

*1* You were proven wrong about that...
*2* I don't HAVE to call stock rotors blanks just to please you!
*3* You called MY posts ignorant? How ironic considering how wrong you are in *4*
*4* I don't even need to say it.. but I will... WRONG AGAIN! :p

And just to be clear, I feel guilty for posting this because I think it overshadows some very good information so I apologize to everyone else, but since you felt so eager to attack me for no reason and try to talk down to me when you were talking out of your ass, and have yet to apologize for the attacks or for calling my posts ignorant (which they absolutely were not) and you still have not admitted you were wrong even after being shown proof, I am allowing myself this guilty pleasure! Thank you for making me laugh so hard when you stated in your last post that you still have not been proven wrong... SO SWEET
:lol:

http://www.threadbombing.com/data/media/32/drama_queen.jpg

Maybe you should put some Lucas Oil on them too. I hear your mechanic says its the shizniz. ;)

[WestAusGTO]

I've read time and time again that drilled rotors are bad, in Fact the DBA web site stipulates that their Drilled rotors are not for track use, so that confirms that they are not for me..
"The unique 'XS' pattern is a premium (advanced) cross-drilled and slotted pattern, providing improved braking performance for street use only" from http://dba.com.au/4000-series

But.. why does every sport motorcycle have drilled rotors ?

[GTOJOE]

I've read time and time again that drilled rotors are bad, in Fact the DBA web site stipulates that their Drilled rotors are not for track use, so that confirms that they are not for me..
"The unique 'XS' pattern is a premium (advanced) cross-drilled and slotted pattern, providing improved braking performance for street use only" from http://dba.com.au/4000-series

But.. why does every sport motorcycle have drilled rotors ?

Bikes use different rotor material I think. Seems to be more like stailness than cast iron.

[DV8]

...and they are mostly non-vented single disk.

FYI ...more good info for the average Joe:
http://www.zeckhausen.com/technical.htm

[hotGTO]

Maybe you should put some Lucas Oil on them too. I hear your mechanic says its the shizniz. ;)

Do you have a crush on me or something? I mean seriously? Quit stalking my posts!

[ChargerX3]

Do you have a crush on me or something? I mean seriously? Quit stalking my posts!

If only you were that interesting. To be fair its hard to not notice an adolescent in the middle of a room screaming, "but whyyyyy...!?"

[hotGTO]

If only you were that interesting. To be fair its hard to not notice an adolescent in the middle of a room screaming, "but whyyyyy...!?"

Grow the fuck up, dumbass!

[stealthee]

Grow the fuck up, dumbass!

Says the guy acting like a 12 year old.

[OhioSpyderman]

Hey hot, how about showing some respect to the SENIOR members?

I've know Max since the first Michigan NG (and maybe before that). He is one VERY technologically INTELLIGENT person....

If I had to choose a handful of members that I would trust in the heat of an argument (or with solving a "systems" issue) Max would be right there at the top....

I'm not saying "bow down" to some of these guys, but take their knowledge for what its worth (and trust me, it's worth a LOT).

Live and learn, grasshopper!

Bob. :)

[GTOJOE]

ah Bob. The resident voice of reason hahahaha. Now get of your arse and make me a short shifter muhahahaha :D

[OhioSpyderman]

ah Bob. The resident voice of reason hahahaha. Now get of your arse and make me a short shifter muhahahaha :D

Did you say the OLD voice of reason? ;)

I'm working on getting a hold of my old partner Tim!!!

Bob. :)

[GTOJOE]

Did you say the OLD voice of reason? ;)

I'm working on getting a hold of my old partner Tim!!!

Bob. :)

Dibs on the first one. I'll pay for it now hahahaha

[hotGTO]

Hey hot, how about showing some respect to the SENIOR members?

I've know Max since the first Michigan NG (and maybe before that). He is one VERY technologically INTELLIGENT person....

If I had to choose a handful of members that I would trust in the heat of an argument (or with solving a "systems" issue) Max would be right there at the top....

I'm not saying "bow down" to some of these guys, but take their knowledge for what its worth (and trust me, it's worth a LOT).

Live and learn, grasshopper!

Bob. :)

You know what? I'm not sure which member is Max that I supposedly disrespected, but look back at this thread, I gave all the respect in the world until I was attacked for asking a legitimate question! ChargerX3 can go mod the other forum if all he's going to do is start trouble, and the other guy totally deserved what I said! You can say I am acting up right now because I am, but only because I was disrespected first so there you go... I was here discussing rotors and some "apparently senior" members (which means NOTHING if you are disrespecting people) who THOUGHT they knew what they were talking about got all pissy because I didn't want to take their word for something and asked for them to show where they got their information, and now are mad because they were wrong! But go ahead and turn it around on me if that gets your rocks off, but if you read how it started I feel pretty comfy saying I don't really care if you all don't like my attitude right now! This is a public forum and if you treat someone like a dog your lucky if he doesn't bite your face off! I have no problem telling any single forum member when he is wrong. And no one else should either! This place is starting to be a JOKE! "Senior members" what a JOKE! To the guys who think "We started 3si, so we should be treated special" keep thinking like that, that's the REAL childish mentality! I've been on this forum starting good threads and asking my questions trying to help build some of the useful information on here and HELP this new forum grow! I don't appreciate being treated like I have been treated in this thread and a couple others especially by ChargerX3, and I feel pretty justified to have a bad attitude right now, so say what you want about me, but I speak the truth!

Edit: Polygon was the other person who I intentionally disrespected because he verbally attacked me for no reason. I have NO problem with Max unless ChargerX3 or Polygon is Max...

[hotGTO]

Says the guy acting like a 12 year old.

I used to respect your posts too.... used to

[naptownvr4]

FWIW I have a friend who works for Panther Racing and I know for a fact they use blanks, not CD or slotted.

[ChargerX3]

The fact is that there are countless members that are on here who have put time, $$$$$$$$, and their souls into the progression of this platform, not site. You are talking about a tight knit group that respects and acknowledges each other. Feel free to object all you like, but be ready to back your claims. Taking a stance with the attitude that "why, everyone else is everyone doing it", or " my mechanic has been using it for years, so he knows better than you" attitude wont fly here.

[hotGTO]

I back up what I say, and so should everyone else! Show me where I have not backed up what I claim? If I question something someone says because I don't know him or his history then he should back up his statement with something substantial! Not just get all pissy because a new member who now owns one of your sacred cars and wants to like it as much as you do questions your logic!

Edit: I should say new OWNER, not new member...

[hotGTO]

The fact is that there are countless members that are on here who have put time, $$$$$$$$, and their souls into the progression of this platform, not site. You are talking about a tight knit group that respects and acknowledges each other. Feel free to object all you like, but be ready to back your claims. Taking a stance with the attitude that "why, everyone else is everyone doing it", or " my mechanic has been using it for years, so he knows better than you" attitude wont fly here.

And why you keep referring to me liking Lucas oil is beyond me!!!! I am alowed to like Lucas oil products as much as you like Mobile 1 or whatever you like!! Get over that!

[hotGTO]

On top of all that, you are talking to a guy who has just spent half a year's salary on a 3000GT AND a stealth in just a matter of months and I am already looking into rebuilding the Stealth motor! If you don't think that's dedication to the platform than I have every right to be pissed off and not care what you think!

[Polygon]

Edit: Polygon was the other person who I intentionally disrespected because he verbally attacked me for no reason. I have NO problem with Max unless ChargerX3 or Polygon is Max...

For the record, I attacked you because you were annoying me. You kept asking the same things over and over again when they had already been explained to you. It wore thin on my nerves. Also, buying two of these cars in the matter of a month with a half of your years salary doesn't make you an expert. To be honest, it doesn't sound too smart. But it does how you are dedicated. Not many people on this forum could be called an expert. I can tell from your posts that you don't know very much about brake systems. And you just kept asking the same crap over and over again, refusing to believe members who have been around a long time and know A LOT more than you. At least until someone came along and posted something that could prove that you're right. Operative word, could. You did nothing to back up your opinion.

I apologize that I got a bit to personal. Perhaps I shouldn't have been such an ass, however, this was a two way street. I wash my hands of this thread as it has turned into nothing more than a drama fest. Perhaps one day I'll get my own tests run and see what turns up.

[GTOJOE]

How about you guys who have issues with each other FTFU or take it elsewhere. You have derailed this thread enough. No one has any interest in personal issues. We are here to read about rotors.

[hotGTO]

For the record, I attacked you because you were annoying me. You kept asking the same things over and over again when they had already been explained to you. It wore thin on my nerves. Also, buying two of these cars in the matter of a month with a half of your years salary doesn't make you an expert. To be honest, it doesn't sound too smart. But it does how you are dedicated. Not many people on this forum could be called an expert. I can tell from your posts that you don't know very much about brake systems. And you just kept asking the same crap over and over again, refusing to believe members who have been around a long time and know A LOT more than you. At least until someone came along and posted something that could prove that you're right. Operative word, could. You did nothing to back up your opinion.

I apologize that I got a bit to personal. Perhaps I shouldn't have been such an ass, however, this was a two way street. I wash my hands of this thread as it has turned into nothing more than a drama fest. Perhaps one day I'll get my own tests run and see what turns up.

See... You got mad because you could not answer my question... And the other person did not prove me right, he answered my question. And I am sorry that this derailed the thread, but I think I did provoke some real information about brakes, and I know a lot more than you think, I just wanted an answer to my question... Sometimes being smart is not knowing the right answer, but knowing the right question! Grasshopper! Just because a person does not know as much about a 3s as you or even about a car as you does not mean you are smarter than him! I bought 2 because I wanted to keep upgrading the NA but took smart advice and invested that cash into a TT, and it was pretty smart so don't hate! And I am also here to discuss rotors, which I was before I was attacked for it! Sorry about everything else....

[TUFFTR]

See... You got mad because you could not answer my question... And the other person did not prove me right, he answered my question. And I am sorry that this derailed the thread, but I think I did provoke some real information about brakes, and I know a lot more than you think, I just wanted an answer to my question... Sometimes being smart is not knowing the right answer, but knowing the right question! Grasshopper! Just because a person does not know as much about a 3s as you or even about a car as you does not mean you are smarter than him! I bought 2 because I wanted to keep upgrading the NA but took smart advice and invested that cash into a TT, and it was pretty smart so don't hate! And I am also here to discuss rotors, which I was before I was attacked for it! Sorry about everything else....
lulwut, yes it does.
Ohhhhh your rebuilding a motor! how dedicated of you!

God you can tell when its school holidays can't ya.

[hotGTO]

lulwut, yes it does.
Ohhhhh your rebuilding a motor! how dedicated of you!

God you can tell when its school holidays can't ya.

Yes, as a matter of fact, good drilled rotors ARE better than "BLANKS" as an upgrade for street usage!

[SkortchGT]

drilled/slotted is a bad idea. more prone to cracking & takes away rotor surface, so there is less pad-to-rotor contact. no reason to go drilled/slotted unless you're hardcore into autocross, then go with a big brake kit.

if you're really concerned about braking performance, get ss braided lines, 2g vr4 calipers all around, stock rotors, a good set of pads, and good synthetic brake fluid, you'll be fine.

[TUFFTR]

Yes, as a matter of fact, good drilled rotors ARE better than "BLANKS" as an upgrade for street usage!


Lol you keep thinking that buddy. I wouldnt touch them if you gave me brand new ones.
For the street;
New fluid, bled of course.
Good bitey pads when hot or cold, I prefer minimal dust ones.
BLANK or if you need some bling, slotted rotors.
And for better feel, S/S lines.

As it's been discussed already, CD's are just asking for trouble, and in no way, shape, or form, are BETTER then a normal disc. You may not think you're ignorant, but from reading all your posts, they scream "I'm a 16yo kid who knows more then you do"

Go put CD's on your car if you havent already, find someone around the area with the EXACT same car/engine/transmission, with the same brake setup, but you with your CD's......Go for a nice twisty drive, and see if your brakes work ANY better then his.

Me and a few mates did a really good test. 2 2004 magna's, identical trim, spec, engine, transmission. Both car's had new fluid.
One car had bendix ultimate pads, Expensive racing fluid, DBA 4000 series slotted rotors front and rear.
Other car had Generic DOT4, Ferodo Zero pads, and machined blank rotors.

Guess what? The car with the extra $550 spent on it's brakes was no better over a 50km stretch of twisty roads then it's cheaper counterpart. That was all the proof I ever needed to see. if 50km of full on hardcore driving wasn't enough to show what expensive fancy rotors and pads can do.......how can some holes in your rotor make it better again?

You keep saying they are "better" with no real proof of how. That's the best proof above of fancy rotors. They weren't CD but you get the idea in terms of fancy rotors claiming to be better for the street.

[bluemax_1]

Wow... the examples some of you guys try to use to make your point.

Tufftr, that's basically saying, "we took two similar, but not identical cars, put completely different parts, pads and rotors on both of them, they weren't racing and we can't even say that their driving skill is comparable, but it proves expensive brake parts are pointless"

Did you even bother reading the posts in this thread?

Now I remember why I really only bother posting technical info on 3stech these days.


Max

[i3igpete]

whats a 3stech? :12:

[hotGTO]

drilled/slotted is a bad idea. more prone to cracking & takes away rotor surface, so there is less pad-to-rotor contact. no reason to go drilled/slotted unless you're hardcore into autocross

You have it completely wrong! You DONT want to autocross with drilled rotors BECAUSE they are prone to cracking under SEVERE usage which is why they are only really an upgrade for STREET usage where they will not see extreme conditions! And they ARE an upgrade from the stock setup and it has already been shown in an SAE report earlier in this very thread! Some of you guys need to read more and learn more and ask more instead of just thinking you already know everything and regurgitating what everyone else thinks is true!!

[thestealth]

This is just my personal experience. I replaced the wore out rotors on my RT several years ago with some decent (ie. middle of the road) cross drilled rotors. Purely from unscientific tests, they did seem to have more clamping force than the the originals. They also chewed through pads a lot faster. Once I sold the car to my 17 y/o son, he was unaware of what the "squeakers" are for on brake pads and trashed the rotors. We replaced them with stock blanks. Stopping power is still just fine. All and all, for me, the marginal increase in stopping power is not worth the expense of having to replace pads twice (give or take) as often for cross drilled rotors.

[hotGTO]

It is true that pads wear faster on the slotted and drilled rotors, so you definitely would have to consider that against the benefits...

[OhioSpyderman]

hot, Max = BlueMax. Yes his real name is Max....

Bob.

[hotGTO]

Hi Bob, Thanks! I never intentionally said anything directed towards Max. As far as I know he has always been pretty knowledgeable and helpful about all kinds of stuff... Thanks!

~Dave

[BjornRune]

A lot of great information in this thread, let's not clutter it with personal agendas. If you don't agree with someones post then fine, but be factual about it. I love you all but seriously.. If I need to read personal insults and slight immaturity I go to 3si :)

To the guys posting tech stuff, thank you. Very interesting read so far.

[Flamer]

Wow... the examples some of you guys try to use to make your point.

Tufftr, that's basically saying, "we took two similar, but not identical cars, put completely different parts, pads and rotors on both of them, they weren't racing and we can't even say that their driving skill is comparable, but it proves expensive brake parts are pointless"

Did you even bother reading the posts in this thread?

Now I remember why I really only bother posting technical info on 3stech these days.


Max

EXACTLY! It's post like those that keep the real discussions and information from being talked about. The majority of page 4's posts were simply bickering and attacking comments; worthless in terms of the technical discussion.

This place is doomed at this rate.

[Atrosity]

This place is doomed at this rate.


Wow so quick to come to that solution when you are barely on here.

[Polygon]

Wow... the examples some of you guys try to use to make your point.

Tufftr, that's basically saying, "we took two similar, but not identical cars, put completely different parts, pads and rotors on both of them, they weren't racing and we can't even say that their driving skill is comparable, but it proves expensive brake parts are pointless"

Did you even bother reading the posts in this thread?

Now I remember why I really only bother posting technical info on 3stech these days.


Max

I have to agree, that's a horrible comparison. It's hardly scientific and the results in no way prove which is better.

[SkortchGT]

You have it completely wrong! You DONT want to autocross with drilled rotors BECAUSE they are prone to cracking under SEVERE usage which is why they are only really an upgrade for STREET usage where they will not see extreme conditions! And they ARE an upgrade from the stock setup and it has already been shown in an SAE report earlier in this very thread! Some of you guys need to read more and learn more and ask more instead of just thinking you already know everything and regurgitating what everyone else thinks is true!!

LOL whatever helps you sleep at night.

[R/T93]

most autocrosses dont see more than 50 mph, its really not that hard on your brakes....

And yes I have autocrossed for 6 years at a relatively high speed track and its not hard on my brakes.

[hotGTO]

Hahahaha.... OK, I finally give up... I submit... I've been taken from all sides... sort out the facts however you want, Effing stupid drilled rotors! Hahahaha

[lawdogg]

One of the things I like most about this community is the % of people who actually race their cars, and understand how and why they work. It's just great to have so many people not only know what they're talking about, but also have seen it and worked on it (and fixed it lol).

[Chris GTO TT]

Hahahaha.... OK, I finally give up... I submit... I've been taken from all sides... sort out the facts however you want, Effing stupid drilled rotors! Hahahaha

The point that you seem to be missing is that while they wont crack as quickly on the street they WILL crack and when they crack they could frag. Then you have no brakes, and at the point you have no brakes you die.

[GTOX]

The point that you seem to be missing is that while they wont crack as quickly on the street they WILL crack and when they crack they could frag. Then you have no brakes, and at the point you have no brakes you die.

But maybe this is the only way?

First hand experience.

Fate.

[Chris GTO TT]

perhaps but people separating the hat from the rotor on 2nd gen brakes is enough for me to choose VERY carefully what rotors i buy for my 2nd gen brake upgrade

[TUFFTR]

Wow... the examples some of you guys try to use to make your point.

Tufftr, that's basically saying, "we took two similar, but not identical cars, put completely different parts, pads and rotors on both of them, they weren't racing and we can't even say that their driving skill is comparable, but it proves expensive brake parts are pointless"


Did you even bother reading the posts in this thread?

Now I remember why I really only bother posting technical info on 3stech these days.


Max

Erm what? The car's ARE identical, With the same braking system, but one has the more expensive things. Both drivers were going FLAT OUT around 50km/h of Australias best beachy roads. If that isn't proof enough of "street" testing, then hell, tell me what is?

[TUFFTR]

I have to agree, that's a horrible comparison. It's hardly scientific and the results in no way prove which is better.

Again buddy - Everyone here is saying "oh on my car it was/was not better then stock"
Best way to actually SEE what's better then stock is to do just that - have 2 indentical cars - in every way - one with the best brakes he can get, the other one with standard stuff. All with new fluid. best way to test how they go? Go for a 50km drive flat out, car behind us did not gain or loose an inch under braking. In my eyes that's the best test. None of this scientific stuff which is always going to be argued anyway.

Now I can say, without a doubt, blank rotor's, DOT4 fluid, and a bitey pad are all you need for the "street"

[Polygon]

Again buddy - Everyone here is saying "oh on my car it was/was not better then stock"
Best way to actually SEE what's better then stock is to do just that - have 2 indentical cars - in every way - one with the best brakes he can get, the other one with standard stuff. All with new fluid. best way to test how they go? Go for a 50km drive flat out, car behind us did not gain or loose an inch under braking. In my eyes that's the best test. None of this scientific stuff which is always going to be argued anyway.

Actually, it's quite the opposite. A true scientific test will not be disputed. What you did was a very unscientific comparison. I would call it speculation hour. While you used two identical cars they had different fluids, pads, and rotors. And both cars driven by different drivers. You had no control and you have to no real way to quantify your conclusion. It's all speculation. If you want to do a proper test here's what needs to be done.

They have brake testing rigs that can apply the same amount of braking every time, that way the results can be quantified and the result can be reproduced by someone else. If not that use an identical car with a professional driver.

Start with fresh fluid, using the same fluid throughout the tests.
Put in new pads, also using new pads with each set of rotors.
Bed the rotors and pads with each test.
Start with OEM blanks as a control.
Then move to the aftermarket blanks.
Then move to the CD rotor which is IDENTICAL to the aftermarket blank in every way except CD. I'm talking they are the same size and the same metallurgical properties.
Don't forget to take the temperature with each run.

That is a how you come to a scientific conclusion. And nobody will ever refute that, if the do they're a moron.


Now I can say, without a doubt, blank rotor's, DOT4 fluid, and a bitey pad are all you need for the "street"

Now, for the majority of people, that's true.

[TUFFTR]

Actually, it's quite the opposite. A true scientific test will not be disputed. What you did was a very unscientific comparison. I would call it speculation hour. While you used two identical cars they had different fluids, pads, and rotors. And both cars driven by different drivers. You had no control and you have to no real way to quantify your conclusion. It's all speculation. If you want to do a proper test here's what needs to be done.

They have brake testing rigs that can apply the same amount of braking every time, that way the results can be quantified and the result can be reproduced by someone else. If not that use an identical car with a professional driver.

Start with fresh fluid, using the same fluid throughout the tests.
Put in new pads, also using new pads with each set of rotors.
Bed the rotors and pads with each test.
Start with OEM blanks as a control.
Then move to the aftermarket blanks.
Then move to the CD rotor which is IDENTICAL to the aftermarket blank in every way except CD. I'm talking they are the same size and the same metallurgical properties.
Don't forget to take the temperature with each run.

That is a how you come to a scientific conclusion. And nobody will ever refute that, if the do they're a moron.



Now, for the majority of people, that's true.

The only problem, is myself, nor alot of people here don't have access to a laboratory to do these tests, which is why, although I understand the flaws in the test, is probably the best way, without a lab coat, to get a good basis of how the brakes are coping under extreme conditions.

I just don't see how, on the street, you can get a better comparo.....do you at least get the point I'm trying to make here?:P

[hotGTO]

The point that you seem to be missing is that while they wont crack as quickly on the street they WILL crack and when they crack they could frag. Then you have no brakes, and at the point you have no brakes you die.

Stock replacement rotors wear out on the street also... All rotors will wear out... as a driver I would know if they were worn out before they ever fragged... I never said they won't crack... I get it though, some of you guys will never use CD rotors, even if they perform better on the street, and there's nothing wrong with that

[Polygon]

The only problem, is myself, nor alot of people here don't have access to a laboratory to do these tests, which is why, although I understand the flaws in the test, is probably the best way, without a lab coat, to get a good basis of how the brakes are coping under extreme conditions.

I just don't see how, on the street, you can get a better comparo.....do you at least get the point I'm trying to make here?:P

Fair enough. Yeah, I can see your point.

[UTRacerX9]

Wow, I missed this whole thread til now. Not going to bother reading all the pages, but I imagine the majority of it consists of a few people saying that cross drilled rotors work better than stock, and other say they don't, and that they are prone to cracking/failure.

A couple points, then my own personal observations.

Porsche, Ferrari, Lamborghini, the Corvette... all use cross drilled rotors. I imagine that their engineers have determined that to get the best braking performance, CD is needed. If not, they are intentionally putting on subpar rotors and endangering the buyers of their products and opening themselves up to lawsuits due to failing CD rotors.

Done properly, cross drilled rotors do not crack with normal, even spirited street use, while giving extra stopping power over full face rotors.

My own personal experience is this, I had a Porsche Boxster S, that came stock with cross drilled rotors. A buddy of mine has a regular Boxster, with a track package and an upgrade to the 911 rotors (which are the same ones that they started putting on the S in 2000, but painted a different color.) Both cars weigh roughly the same. The kicker, he chose to go with full face rotors because he autocrosses a lot. Well, we didn't do any fade testing or anything like that, but we were curious to find out which car had greater stopping power, because I believe that CD rotors offer better braking performance for the street, and he thought otherwise.

So, we lined them up in a parking lot, and marked off increments from 100ft to 130ft with cones. We knew we'd stop somewhere in that range doing 60-0. So we each ran about 4 times, driving 60mph, then braking when we hit the marker we set. The difference was small but significant, my car came to a stop about 4-5 ft shorter than his on every run. And, this is with me using the stock brake fluid, and him using ATE200 (which should have helped him.) Then, we also wanted to see what would happen if we did the run from 80mph. We weren't able to be as scientific on this one, because the parking lot didn't have enough room for it, but we found a long quiet street in a new neighborhood and did two runs from 80. It was an even bigger difference the first time, about 10 ft, and about 5 feet the second time. Since we didn't have everything marked off and all that, it's not as accurate, not to mention slight differences between when we actually hit the brakes as we passed the cone, but there wasn't a single time that he was able to stop his car in as short a distance as mine.

[hotGTO]

Wow, I missed this whole thread til now. Not going to bother reading all the pages, but I imagine the majority of it consists of a few people saying that cross drilled rotors work better than stock, and other say they don't, and that they are prone to cracking/failure.


LMAO! Yeah, in a nutshell, exactly!! With plenty of heated discussion mixed in for good measure. LOL! There is reference to an SAE report that compared CD to blank rotors that also came up with similar results to your street test... That's a pretty interesting test you did, do the 2 cars weigh the same?

[bluemax_1]

Several points to note:
Tufftr, the reason your test is invalid and of little use is because there were way too many variables, the drivers being the biggest ones. I've outrun a Transam on a racetrack with my VW Golf GL. Does that mean I go around claiming that the Golf is, without a doubt, a faster car around a racetrack? No, it means the other guy sucked.

I've driven a car round a racetrack that the owner had brake fade with. I ran faster laps without fading the brakes. I'm not talking about pseudo identical cars with completely different brake components, I'm talking about the exact same car, 30 minutes after the session where he had brake fade, on the exact same track. Does that mean the brake fairy blessed the brakes before I took his car out with the extra weight of both of us in the car as opposed to just him when he faded his brakes? No, it means his braking technique sucked (as well as his cornering). One of the first things that instructors end up teaching novices to the track is proper braking technique. It usually makes them faster and reduces the abuse on their brakes.

At least utracerx9's testing methodology was more consistent. In order to ensure that the results were viable though, a couple of variables would have made the results more worthwhile, i.e. using the same exact car and just swapping out the rotors, but since this is too much of a pain for the average Joe, at least ensuring that the cars had the same tires (same type, age, durometer and tread depth) and the same 'race' weight, plus a GPS based system or even a Gtech Pro to discount differences in brake application.

Several things to note about Utracerx9's tests, as has been mentioned before, ultimately, a car's tires determine its stopping distances. Once the brakes generate enough torque to trigger the ABS system, the brakes are generating enough brake torque to stop the car at its particular (for the tires) maximum rate of deceleration. The difference will be between which tires maintain traction better before they begin to slip (thus activating the ABS) vs. the tires that begin slipping sooner and activating the ABS sooner and longer.

Using higher mu brake pads, you can increase the brake torque, but if you're already at the tire's grip limit, you will not be stopping in a shorter distance because the higher mu brake pads will simply be able to lock up the tires with lower pedal effort. They won't really slow the car down faster, because you're still limited by the tire's ultimate grip and traction.

Now brake fade will become a factor after numerous stops (or stops from higher speeds) where the thermal capacity of the system (mass of the rotor= heatsink), thermal transfer efficiency (how well the system transfers heat to the air) and how well the system resists pad fade and fluid boilover, but if one car consistently stops shorter from the first to last braking event and both cars can trigger their ABS, that indicates tire traction differences more than anything.

One interesting point to note from the SAE paper:
The testing indicates that solid blanks actually exhibit higher brake torque than crossdrilled rotors at lower temperatures (this appears to be where the greater surface area WITHOUT the holes is a factor). At medium to higher temps though, the crossdrilled rotors begin to generate higher brake torque, and the drilled rotors exhibit more consistent brake torque vs. temp than the blanks.

The above data demonstrates the drilled rotors' interaction with the edges of the holes. When the pads are cold and hard, they don't interact with the edges of the holes (or slots) much, so the greater contact surface area of the blanks generates higher torque. When the pads heat up though, as I mentioned before, the pad surface, under the extreme pressures of a braking event, become more malleable and actually press into the holes/slots and there is mechanical interaction between the pads pressing into the holes and the rear edge of the holes increasing 'bite' into the pad (and as such, also wearing it faster). This results in increased brake torque at higher temps. Regular slotted rotors will not show as significant an increase in brake torque (vs blanks) because they do not have as much 'edge' area interacting with the pad surface as the average drilled rotor. J-hook designs though, generate similar increased brake torque at higher temps due to the greater edge area under the pad.


Max

P.S. another interesting thing about drilled vs non-drilled from the SAE paper. They noted that in the wet, the drilled rotors generated higher torque and shorter stopping distances with MILD to moderate brake application, BUT when he brakes were applied hard as they would be for someone trying not to hit something, there was no difference between drilled vs non-drilled. At the higher pedal effort, the pressures generated at the pad-rotor interface were enough to squeeze out the hydrodynamic fluid film layer between pad and rotor, so the holes make no difference, except under mild braking with lower pressures.

P.P.S. as far as the age old argument of, "Well XX, YY and ZZ manufacturers put them on their top of the line sportscars, so they must be great". A retired engineer from a sportscar manufacturer told me that they tried selling cars with blanks before. Problem was, the average buyer tended to be older (to afford the cars) and they had an old mentality retained from when crossdrilled rotors were necessary to combat pad outgassing. Their marketing guys discovered that potential buyers would look at the cars in the showrooms and go, "You'd think for the price, they could at least put crossdrilled rotors on these". Even if (and especially if) the cars were meant to be taken to the track. So the marketing guys realized, give the customers what they want. They made the rotors bigger (to compensate for the reduction in mass) and put crossdrilled brakes on all their cars.

Now, from the SAE paper, we can see that there IS a tangible benefit from crossdrilled rotors for a mostly street driven car, but what about for cars that are marketed as being track toys? For a perfect example, take the R35 GT-R. Now we ALL know about the marketing for this thing with the Nurburgring times, Top Gear and other track tests vs. 911 Turbos etc. You know what happens when you take a showroom stock R35 with it's massive crossdrilled brakes to the track? Yep, Jack T's car is not an exception, it's the rule. The massive crossdrilled rotors on the R35 crack when used on track. One of the first upgrades for track use is to get better pads and to buy some J-hook APR rotors (or other non-drilled rotors).

Funny thing is, it seems this oldschool mentality is alive in other areas as well. Ever wonder why some tires still show a Z-rating on the sidewall? Same thing, marketing for the older, less technically up to date folks. Now any of us who are into tires are well aware that W and Y ratings are higher than Z. So why do some manufacturers still put 265/35ZR18 92Y on the side of a tire? Why not just 265/35R18 92Y? Or 265/35YR18 92?.

There are fewer tire companies that do this now (although there are still some), but the reason was that when they came up with the higher W and Y speed ratings, many owners (especially the older ones) weren't up to date on tire spec. All the knew was that tires had speed ratings. H was low, T was better Z being the last letter of the alphabet was best. Some of these old codgers would look for that Z-rating and if it wasn't there, they'd immediately discount the possibility of using it on their performance car. W and Y being lower than Z (in their minds) meant those tires weren't 'top-of-the-line'. So the manufacturers left the ZR there for these clueless folks.

[UTRacerX9]

LMAO! Yeah, in a nutshell, exactly!! With plenty of heated discussion mixed in for good measure. LOL! There is reference to an SAE report that compared CD to blank rotors that also came up with similar results to your street test... That's a pretty interesting test you did, do the 2 cars weigh the same?

Maybe 100lb difference at most.

[Chris GTO TT]

Stock replacement rotors wear out on the street also... All rotors will wear out... as a driver I would know if they were worn out before they ever fragged... I never said they won't crack... I get it though, some of you guys will never use CD rotors, even if they perform better on the street, and there's nothing wrong with that

There is a difference between wearing out (which is 100% normal) and cracking and having the rotor physically fall apart. I've personally seen cars that were only driven mildly on the street with cross drilled rotors with significant cracking radiating away from most of the holes in drilled rotors. Once the rotors begin to crack you MUST replace them. While blank faced rotors can be resurfaced 1-2 times over about 3-4 times as many miles.

[Flamer]

Once the rotors begin to crack you MUST replace them. While blank faced rotors can be resurfaced 1-2 times over about 3-4 times as many miles.

To be more specific, as long as the blank faced rotor is within spec it can be resurfaced/turned.

[UTRacerX9]

Max, we were both running the same size tires, 225 front, 265 rear, and the same brand, Continental Sport Contacts. My car had fairly new tires on it, about 2-3k miles, not sure how many his had but tread depth difference was slight. (He ran another set of wheels and race tires for autocross.) He also had stock 18 Porsche turbo "twist" wheels, and I was running some 18" factory upgrade wheels, not sure of any weight difference, but I don't think it would be significant.

I agree with everything else you are saying, but it's simply a fact borne out in real world testing from the SAE specs and my own somewhat scientific findings that show CD rotors are better for the street. For the track, I'd rather have solids/slotted.

[bluemax_1]

UTRacerX9, yep, there are definitely benefits to CD rotors for street use, I was just pointing out that if your testing demonstrated that one car stopped in a shorter distance than another from the first stop to the last, it tends to indicate that one car has better tire traction than the other. Different wheels can make a difference if they alter the rotational inertia, because it affects how well the wheel is slowed and how the ABS triggering affects it. The lighter the rotating assembly, the better.

The reason I have a durometer is to track the durometer/hardness of the tires, especially after moving to R-comps in the summer. I even noticed the traction difference on street tires measuring the deceleration limits with a GTech Pro RR on friends' cars with tires that had similar tread depth, but different durometer. They were both running cheapo Kumho Ecsta tires of the same width on a pair of Miatas, 1 had new-ish tires and the durometer measured about 73 on the Shore A scale. The other car had older tires with similar tread depth, but the tires were a couple of years old (the guy doesn't drive the car much except on weekends), and the same Ecsta tires measured about 75-76 durometer.

Just for the sake of comparison, my Yokohama Neova AD07's measured 70 durometer at ~70f, and my A048's measured about 65 durometer at the same temps. The amazing thing is that even after several thousand miles of street and track driving, the AD07's still measured about 70 durometer at 70f. Haven't had the chance to seriously track the A048's recently, but from a couple thousand miles of street driving, they still measured about 65 durometer at 70f, so as R-comps go, they aren't too bad at resisting heat cycling (unlike Hoosiers which can heat cycle out in one weekend of track use even though there's still decent tread depth remaining). Then again, I haven't driven the car (or measured the A048's durometer) in over a year, as it's still on jackstands.


Max

[hotGTO]

Definitely good information... What about just using a more grabby set of pads instead of CD? Do the grabbier pads wear out faster, and wouldn't replacing pads more often be better than replacing rotors? Would you actually increase the life of the rotor because of softer pad material putting less stress on the rotor?

[Polygon]

Definitely good information... What about just using a more grabby set of pads instead of CD? Do the grabbier pads wear out faster, and wouldn't replacing pads more often be better than replacing rotors? Would you actually increase the life of the rotor because of softer pad material putting less stress on the rotor?

Actually, quite the opposite. The more aggressive the pad the more you're going to be replacing rotors. They don't work like tires where the softer material has more grip. The best comparison I can think of right now is to sandpaper. The more aggressive pads are more like lower grit sandpaper. The more aggressive they are, the faster they chew up rotors.

[hotGTO]

That makes perfect sense...

[bluemax_1]

Actually, quite the opposite. The more aggressive the pad the more you're going to be replacing rotors. They don't work like tires where the softer material has more grip. The best comparison I can think of right now is to sandpaper. The more aggressive pads are more like lower grit sandpaper. The more aggressive they are, the faster they chew up rotors.

That's nice, but it's wrong.


Friction compounds used in brake pads these days can be divided into two basic categories: Abrasive and adherent.
Few good brake pads function (at optimal levels) on abrasive friction these days. Most of the good pads are based on adherent friction.

The abrasive friction pads, as the category suggests, work as Polygon describes, in a manner somewhat akin to sandpaper, but still not quite.

The adherent pads work by forming chemical bonds. The way they work is as such:
The pad material forms bonds best to itself. You could say that it works in a manner similar to certain kinds of contact cement. Eg. say you wanted to stick two boards together, if you apply the contact cement to one board and press the boards together, they will stick together but the bond is not very strong. The appropriate way to apply it, is to apply a thin layer to each board, allow them to dry somewhat till the layer is tacky, and then press the boards together. THIS creates a much stronger bond. If you applied the cement to just one board and allowed it to dry till tacky and stuck the other board (without any cement on IT) to the first board, the bond between them would be even weaker.

The pad material activates above a certain temperature so you need to heat the brakes up and apply a layer to the rotors. Once this layer has been applied and allowed to cool, when the brakes are applied, the pad material layer that has since bonded to the rotor face now activates to bond to the pad layer on the pad face. The bonding and breaking of the bonds generates the heat that is the conversion of kinetic to thermal energy that slows the car down. As the pad material is heated, the bonds are created and broken and the pad also continually leaves a thin film of itself on the rotor. With many of the newer good adherent pads, you can track the car a whole lot and go through many sets of pads and the rotors will still be in great shape. The reason to have 2 sets of rotors for street and track on dual use cars is so you won't have to keep bedding in different compounds for different uses, or use a less than ideal compound which might eat the rotors on the street, or be inadequate on track.

Abrasive pads don't leave deposits, they grind them off, so if someone tells you that rotors don't warp, the phenomenon is actually uneven pad deposition, but pads work on abrasive friction, you can infer that their information is incomplete.

Ever wonder why you need to bed-in pads? The main reason these days is to deposit a proper pad material layer on the rotors for the purpose of properly functioning adherent friction.

In the old days, you needed to gas out pads to avoid green fade. This is the reason old racers spoke of literally BBQ'ing their brake pads. The pad compound is held together by resin, when the pads are first subjected to a lot of heat, the excess resin could (would) bleed out and the goo would get between the pads and rotor and result in VERY little friction. You could stand on the damn pedal, it would feel hard as a rock (as opposed to fluid fade/boilover where your pedal goes to the floor) but the car wouldn't slow down. So they put the pads in a BBQ and baked out the excess resin before bedding them in.

BTW, this old BBQ trick still works on new compound/composition pads these days. If you use the BBQ trick, bedding in goes a lot quicker. In another thread I described the bedding in process with brand new pads and rotors. You accelerate to ~65mph, brake at about 70% down to about 10mph(without ever stopping completely) then accelerate back up to 65mph, repeat about 8 times and that will bed most street pads, but while bedding in the pads, you will find that from braking events 1-3 your brake torque is about 5-6 on a scale of 1-10 for that pad. From braking events 3-6 though (depending on the pad), your brake torque will DROP to 2-4 on a scale of 1-10 and feel like you're losing your brakes (pedal will be firm, but for the same pedal pressure, the car doesn't decelerate very well). This is an example of the excess pad material binder bleeding out and burning off. As you continue the bedding process, from stops 6 to 8, you will feel the brake torque start increasing to 9-10 on a scale of 1-10 and the car will now be decelerating much harder/quicker for the same pedal pressure. If you stuck the pads in the BBQ for ~15 minutes when the BBQ is nice and hot, you won't experience the reduction in brake torque from braking events 3-6. All you have to do is get the pads hot enough to begin leaving a nice pad deposit layer and it'll only take about 4-6 braking events (depending on the pad).

edited to add info, post to long, continued in post below


Max

[hotGTO]

I'll definitely be doing that little rust test after bedding in a new set of pads and rotors... a couple months away...

[Lithium]

If you get them hot enough the rust seems to just fall off or turn white.

[Atrosity]

Bluemax just wrote a novel about brakes. ;)

[OhioSpyderman]

Bluemax just wrote a novel about brakes. ;)

THAT is because Max is VERY intelligent :)

Bob.

[bluemax_1]

continuation of post #186


Now keep in mind that ALL adherent pads have an optimal thermal range where the pads function best in adherent friction and leave an appropriate material layer down on the rotor surface. Street pads tend to have a narrower optimal operating temperature range which is lower down the temp scale (because they need to work even when cold and in the middle of winter). Race pads on the other hand tend to have higher mu (coefficient of friction), a wider effective temp range and a higher MOT (Maximum Operating Temperature). This tends to come at the cost of a higher Minimum Operating Temp, i.e. many race pads don't work under adherent friction below a minimum temp (eg. 250f for many race pads and even higher for some). Also bear in mind that even adherent pads are going to be somewhat abrasive. No friction compound works in the completely adherent zone, a little abrasion will help keep rotors even s the pads can function best. The best pads though, as mentioned, will look like their hardly wearing the rotors at all even after several track events and pad changes. BUT a pad that functions mostly under adherent friction within its optimal temp range may be mostly abrasive below that optimal temp range.

Now take Hawk Blues for instance, a fairly old pad as compositions go (been around a while). Hawk Blues are actually decent pads for roadcourses (and racing lighter cars), but if you try to use them for street driving, they will do 2 things:
1) They'll have a lower coefficient of friction than even some cheapo Autozone pads when cold (if you needed to slam on the brakes to avoid the dumb kid who ran in the middle of the street after his ball, you'd have to REALLY stand on the brakes). The mu will of course be WAY lower than when the pads are hot, on the track.
2) Because they are for the most part, below the adherent friction temp threshold, they will be functioning on abrasive friction and will grind the shit out of your rotors within a short span (100 miles or less) of street driving them. Incidentally, this particular phenomenon is why StopTech actually recommends street driving Hawk Blue pads for a specific purpose; to remove the pad layer from rotors before swapping to different pads (for track nuts who use different pads with only one set of rotors), because it's easier than removing all the rotors and having them turned before bedding in the different compound (and is just as effective).

BTW, the pad deposit layer is also the reason why it's generally not a good idea to swap between pad compositions without changing the rotors or having them turned (or grinding them by street driving Hawk Blues). You won't be able to properly bed-in the new pads if there is a layer of pad material from a different composition and since adherent pad materials stick best to themselves, you'll have much lower brake torque too.

I can personally attest to the fact that Carbotech pads will NOT bed-in properly over Hawk pads. The mu/brake torque was SO much lower, it was ridiculous. Lesson learned, don't be cheap/lazy, do it right. No biggie, I won't ever be going back to Hawk pads for the street anyway. Carbotechs are better in just about every respect. Cool thing is, if you use Carbotech pads, you can bed-in their race pads over their street pads and vice versa without turning the rotors.

There are pads that are aggressive to rotors and there are pads that are gentler to the rotors. Some of the aggressive pads are aggressive in different ways (i.e. they will grind the rotors) and you'll see this by the rotors being very worn after track use (where the pads should be operating in the adherent zone). Other pads can be aggressive to the rotors by generating a lot more heat (and trapping it under the pad layer on the rotor surface), these pads will cause a LOT of micro cracking in the rotor surface (but that's not necessarily a bad thing because they are just surface cracks, they don't seriously compromise the structural integrity of the rotor). Some of the best race pads generate ridiculously high mu (for use ONLY with race compound tires. With street tires, they'll just lock the wheels or trigger the ABS at the drop of a hat), but are actually very rotor friendly. The downside is, the pads might wear faster.

Now here's a funny tidbit that should in theory have a whole bunch of curious people heading outside to inspect their cars:
You can check to see if your pads are properly functioning under adherent friction with this simple test. Good pads functioning on adherent friction leave a thin film of pad material on the rotor. This pad material layer tends to inhibit rust formation (obviously, I'm talking about the swept area of the rotor). If your rotors show rust from the car sitting undriven for a few days, your pads are NOT working on adherent friction. If they aren't functioning on adherent friction, the rotors will in fact, show rust overnight if it rains. Just for info, the Carbotech Panther Plus and Bobcat combo I use on the street is now showing some surface rust spots,... after the car has been sitting on jackstands over a year! The PP compound, which is now the AX6 needs a little more work to maintain the pad layer. I needed to brake fairly hard every so often to ensure a decent pad layer while street driving.

Capisce?


Max

[Lithium]

Leave those rotors in New Mexico and I bet they will rust in a month.