Kevlar timing belts vs OEM timing belts... thoughts?

[92RT-TT]

I'm just trying to get people opinions on the pros and cons of running an OE belt vs a Kevlar belt? The only negative things I've heard about the Kevlar belts are that they are rather unforgiving if you have a solid tensioner.

What are people's experiences with them?

[AdamVR4]

I've had nothing but good luck with mine, but I have a stock valve train and only spin it up to 8030 RPM.

As far as I know, until Ray had a random failure with an OEM belt, it was widely thought that there was no reason to use the kevlar belt.

This is the next belt I'll be using: Gates Racing Timing Belt Mitsubishi 3000GT - T195RB (http://www.customcarscentral.com/gatt195rb-mitsubishi-3000gt.html)

Are you going to use aftermarket valve springs?

[vr4tune]

coopkill changed kevlar to OEM his because it made noise. I think that it may be a isolated incident not sure I have no experience other than OEM.

[AdamVR4]

coopkill changed kevlar to OEM his because it made noise. I think that it may be a isolated incident not sure I have no experience other than OEM.

And yes, some people complain about squeaking and the blue rubbing off on pulleys. That issues seems to be hit or miss. With the cost of the kevlar belts today, I'd go with the gates belt... That's assuming you're going to run aftermarket valve springs/cams/rev past 7K.

[vr4tune]

I spin 8200 on a OEM belt and 3sx valve springs on a DD for a year now.

[AdamVR4]

I spin 8200 on a OEM belt and 3sx valve springs on a DD for a year now.

And there's nothing wrong with OEM, either :) All we've got is very limited anecdotal evidence. It would be great to see some tension test and CMM (or however the heck you would accurately measure a belt) comparisons.

[green-lantern]

Aaron works for a belt company so he knows a good bit about it. He will probably chime in.

[UTRacerX9]

I think it's practically a moot point. Most people who have modified their car to the point where they might actually NEED a kevlar belt usually blow up their engine/tranny long before needing to change belts, whether it's an OEM one or not, and then they replace it for the rebuild.

[stealthee]

99.999% of the time the belt isn't the failure point in the timing system. A tensioner fails, water pump seizes, etc and causes catastrophic failure that even a kevalr belt won't stop. No point in spending the extra coin on kevlar.

[HilbillyHomeboy]

My opinion is it's a waste of money. Yes, I owned one. OEM gets the job done perfect, at a fraction of the cost.

Jeremy

[AdamVR4]

@ Cherry Hill, the OEM timing belt is $133.51... Barely cheaper than the gates racing belt.

I do agree though, it's hard to justify anything other than OEM today.

[HilbillyHomeboy]

That's got to be a msrp price, unless the price has skyrocketed in the last few years. I wasn't paying anywhere near that for them.

Yeah, I jumped on the Kevlar wagon when they first hit the market. After consideration, it just wasn't worth it, so I switched back to the OEM belt.

Jeremy

[92RT-TT]

Thanks for the info guys. I think OEM will be just fine then or that Gates one. I am planning on running High tension valve springs and 280 Crower cams but I dont plan to spin the motor past 7k.

[aaronatstate]

Just an FYI, the Kevlar belts, at least when it comes to Gates, is not the tensile member (the cord), but rather the fibers in the Jacket material (what actually makes contact with the pulleys), and there is Kevlar fiber in the rubber compound to make it stronger. This is also why they make more noise, because those fibers don't give as much when it contacts the pulleys, leading to higher noises. But the Kevlar fibers make the jacket material last a lot longer. The fibers in the rubber, and therefore the tooth make it a lot stronger.

The Gates timing belts for the 6G72 are made in Japan. Both standard label and the racing belt version. I know here in America we actually use blue rubber to make the belts, but in Japan they use black rubber, and paint the back of the belt blue, which is why blue comes off on the pulleys sometimes.


And there's nothing wrong with OEM, either :) All we've got is very limited anecdotal evidence. It would be great to see some tension test and CMM (or however the heck you would accurately measure a belt) comparisons.

Definitely do tension tests, along with various other tests on an Instron to determine the belt strength. Also we have various dynamic and life tests we do as well. As for measuring the dimensionals, its pretty straight forward. Length is done a machine with 2 equal size pulleys, width is done with a caliper, and thickness is done with a caliper or modified snap gage.



As for my personal recommendation for which timing belt to use? It would go in this order.

Least Desirable - any non-brand name. These are made by major belt makers, but with cheaper materials.

Next Desirable - any Brand name belt. These are made to meet or exceed OEM standards, and they do. Just as an FYI, the Gates Label, NAPA Label, and Carquest Label belts are all identical, except for the label on the belt, and the box they come in. Made with the same materials, on the same mold, and sometimes even at the same time.

Next Desirable - OEM. OEM belts have the best standard materials in them. This is why they are more expensive then regular aftermarket belts.

Most Desirable - Gates Racing. These belts have the best materials in them period. The rubber is designed to exceed OEM performance by up to 300%. They have the strongest tensile member, the best jacket material, and the strongest rubber. These belts are incredibly strong.

[DuTTch]

My Kevlar belt stretched on me. OEM or Gates FTW

[93SlugTT]

i went to a gates belt.

[aaronatstate]

I would say that OEM or brand name replacement (Gates, NAPA, CarQuest, Dayco, Goodyear, Conti) are good enough for about 90% or more of the people on this board. The other 10% I'd recommend the racing belt too (high hp applications, or people who do a lot of racing). Of course you can't go wrong with the racing belt either.

[AdamVR4]

My Kevlar belt stretched on me. OEM or Gates FTW

How do you know that?

[Vantage]

I've had no squeeling or anything yet from my Gates Racing belt. **KNOCK ON WOOD**

[aaronatstate]

How do you know that?

I to would like to know. Timing belts should not stretch more than a .001 to .002". The fiberglass cord in them has an extremly high modulus.


I've had no squeeling or anything yet from my Gates Racing belt. **KNOCK ON WOOD**

Sweet! Another thing that can cause noise, is if there is too much rubber bleed through through the jacket. It doesnt make the belt bad at all, but it can make them noisier.

[92pearltt]

Some good info in this thread.

[fullracegt]

I know this is a little off topic,but what are the pros and cons of using a solid timing belt tensioner?

[AdamVR4]

I know this is a little off topic,but what are the pros and cons of using a solid timing belt tensioner?

pros - won't be overwhelmed by stiffer aftermarket springs, less likely to allow the timing belt to jump due to violent miss-shift
cons - difficult to achieve stock belt tension, won't compensate for belt stretch, may require more frequent inspection

[ruben2566]

The stock belt in my KIA motor had a Gates logo on it along with several KIA logos, which led me to believe it was made by Gates.

[aaronatstate]

The stock belt in my KIA motor had a Gates logo on it along with several KIA logos, which led me to believe it was made by Gates.

It is, at our plant in Korea. The OEM belt anyway. We make an aftermarket one here in the States too. Matter of fact I was just messing around with them the other day!

[Tigchamp]

So, as I have both.
What is the problem with having a Kevlar belt & a Solid tensioner.
Jeff

[aaronatstate]

I personally would never run a solid tensioner knowing what I know about belts now. No system that a belt runs is perfect. Nothing is aligned 100% perfectly. This leads to a few thousandths of length variation as the belt rotates. (When we measure them at work we might see the belt length change from .002 to -.001 for example). They tensioner is there to take up the length variation. With a solid tensioner you don't get that.

[Chris@Rvengeperformance]

Need a "solid" tensioner with a spring in it.