Stock Caliper BBK Kits

[Disrupter]

Oh I meant I just got dimpled and slotted rotors put on and have about 50 miles on them with Hawk pads. Would be a waste to just swap them out, I will buy your kit to have when I burn through my current setup. I do want to try out some road course, drag, and autox.

[sergechronos]

the brake bias change is fairly minimal. on a 1g is basically a 4% shift to the rear based on rotor sizes. on a 2g its a little over 5%. all in all the slight change to the rear actually helps reduce brake understeer.

adding a proportioning valve on an abs system doesn't work the best. it is easier to adjust the feel with a brake pad change. if you feel the rear is braking to hard, you can change the rear to a less aggressive pad or change the front to a more aggressive pad.

overall it is a small change and does not change the braking feel really on the car, just adds a lot more braking.

Would require actual measurement of where the midpoint of the braking area on the larger rotors would be compared to the stock pads. Upsizing the rotor moves the point outwards, assuming that all else stays the same, this changes the forces dramatically. If we assume a single piston design for the rears, the coefficient of friction times the force applied times the radius determines the torque generated (and in effect the brake bias.)

On a 1G car with the same effective front and rear brake rotor radius and factory prop valve (with a working ABS system) increasing rotor diameter should add probably 20-30 percent more brake torque to the rear than before, the fronts would get a larger increase since the prop valve doesn't effect them (ie, they still get the 1100psi generated with the brake booster, where as the rear is increasing in a non-linear function after approximately 600psi) so probably safe to say that the fronts would generate and increased brake torque of at least 30%.

Assuming the front is generating a clamp load of 9304.75lbs, a coefficient of friction of .45 (reasonable assumption for OEM) for two pads gives us 8374.27. Factor in the mid point of the braking face as the radius for the torque, you get about 3.75" for the factory, and approximately 6" for the 370Z (in class so can't measure till I get home from work late tonight) which means about 1/3', and about 1/2' radius (conversion gives us result in matching units to provide ft/lbs) for a final brake torque of approx 2471ft/lbs stock for a 1G, and 4187.135 with the 370Z rotors (which would be close to a 60% increase.) 2Gs would likely see close to a 30% increase in braking torque (don't recall off hand what their rotor size is, 10" or 11"?)

The rears don't see such a substantial change as they have a smaller total piston diameter (with a single 1 1/2" on 1G rears, and a pair of 1.5" on 2Gs) and obviously less pressure.

Even at 1100psi, you're looking at a clamp load of 1943lbs for a 1G, and 3886lbs for a 2G.

Assuming same .45 coefficient of friction, and the radii will also be roughly the same, you're looking at about 273ft/lb 1G, approximately 1092.93 for a 2G.

Moving the radius out for the larger rotors, you get
about 437.175 ft/lb for a 1G
about 1748.7 ft/lb for a 2G

Obviously, actually being able to measure would make a difference (since ball parked at just under 10" for the 1G fronts and right around 14" for the 370Zs, as would the real line pressures heading to the calipers in the rear (since that alters the clamp load for the rear.) Rear difference should be closer together since they don't get full line pressure, as is it's 50-60% difference from stock. Overall brake bias shouldn't be unbearable if doing all 4, however I don't know that you will get a compound with a big enough coefficient of friction difference to compensate. a .5CoF (which would be rather high) on the front would net 4652ft/lbs with the Z rotors, and going as low as a .4 CoF (if there is such a thing) puts you at 3791.5ft/lbs. It'd require knowing the coefficient of friction for whichever pad you go with and doing the math to determine that the ratio between front and rear stays approximately the same or nearly, as well as the expense of trialing different combos to find the one you like, to say nothing of the fact that generally high CoF compounds are race style compounds that require heat to perform at that level and as such may make for an unsettled (or uneven) experience.

Of course, setting prop valves isn't a safe and easy matter either since it requires high speed braking with an untested set up.

All that said, for those wishing to do a complete swap and who have already exceeded the limitations of the stock rotors, this is a great solution without the expense of a full on BBK. If someone else wants to do the actual measurements on rotors and pads and such to do the math and determine it all, that'd be great. Or of course, if there's formula or results that I've gotten wrong, please feel free to point those out as well so that we can make sure that all that we have is correct info (since there's not a ton of it out there for the brakes or these kinds of upgrades.)

[green-lantern]

Jeremy?

[flewis763]

Would require actual measurement of where the midpoint of the braking area on the larger rotors would be compared to the stock pads. Upsizing the rotor moves the point outwards, assuming that all else stays the same, this changes the forces dramatically. If we assume a single piston design for the rears, the coefficient of friction times the force applied times the radius determines the torque generated (and in effect the brake bias.)

On a 1G car with the same effective front and rear brake rotor radius and factory prop valve (with a working ABS system) increasing rotor diameter should add probably 20-30 percent more brake torque to the rear than before, the fronts would get a larger increase since the prop valve doesn't effect them (ie, they still get the 1100psi generated with the brake booster, where as the rear is increasing in a non-linear function after approximately 600psi) so probably safe to say that the fronts would generate and increased brake torque of at least 30%.

Assuming the front is generating a clamp load of 9304.75lbs, a coefficient of friction of .45 (reasonable assumption for OEM) for two pads gives us 8374.27. Factor in the mid point of the braking face as the radius for the torque, you get about 3.75" for the factory, and approximately 6" for the 370Z (in class so can't measure till I get home from work late tonight) which means about 1/3', and about 1/2' radius (conversion gives us result in matching units to provide ft/lbs) for a final brake torque of approx 2471ft/lbs stock for a 1G, and 4187.135 with the 370Z rotors (which would be close to a 60% increase.) 2Gs would likely see close to a 30% increase in braking torque (don't recall off hand what their rotor size is, 10" or 11"?)

The rears don't see such a substantial change as they have a smaller total piston diameter (with a single 1 1/2" on 1G rears, and a pair of 1.5" on 2Gs) and obviously less pressure.

Even at 1100psi, you're looking at a clamp load of 1943lbs for a 1G, and 3886lbs for a 2G.

Assuming same .45 coefficient of friction, and the radii will also be roughly the same, you're looking at about 273ft/lb 1G, approximately 1092.93 for a 2G.

Moving the radius out for the larger rotors, you get
about 437.175 ft/lb for a 1G
about 1748.7 ft/lb for a 2G

Obviously, actually being able to measure would make a difference (since ball parked at just under 10" for the 1G fronts and right around 14" for the 370Zs, as would the real line pressures heading to the calipers in the rear (since that alters the clamp load for the rear.) Rear difference should be closer together since they don't get full line pressure, as is it's 50-60% difference from stock. Overall brake bias shouldn't be unbearable if doing all 4, however I don't know that you will get a compound with a big enough coefficient of friction difference to compensate. a .5CoF (which would be rather high) on the front would net 4652ft/lbs with the Z rotors, and going as low as a .4 CoF (if there is such a thing) puts you at 3791.5ft/lbs. It'd require knowing the coefficient of friction for whichever pad you go with and doing the math to determine that the ratio between front and rear stays approximately the same or nearly, as well as the expense of trialing different combos to find the one you like, to say nothing of the fact that generally high CoF compounds are race style compounds that require heat to perform at that level and as such may make for an unsettled (or uneven) experience.

Of course, setting prop valves isn't a safe and easy matter either since it requires high speed braking with an untested set up.

All that said, for those wishing to do a complete swap and who have already exceeded the limitations of the stock rotors, this is a great solution without the expense of a full on BBK. If someone else wants to do the actual measurements on rotors and pads and such to do the math and determine it all, that'd be great. Or of course, if there's formula or results that I've gotten wrong, please feel free to point those out as well so that we can make sure that all that we have is correct info (since there's not a ton of it out there for the brakes or these kinds of upgrades.)

yes there is so many variables it is hard to say exactly. I basic numbers are just off rotor size overall different generating an increase in leverage. as for the center of the caliper difference that is simple, all the brackets are just one minus the other divided by 2. so a 2g from would be 355-314=41/2=20.5mm. that how far the caliper center moved up. id have to measure what the oem center is though. pad friction can play a huge roll in the real world calculation of it as well. overall though it is not a huge difference and is much better than just going a large front upgrade only. that can cause bad braking understeer.

overall it is a pretty good package. its not really a track setup but for an aggressive street driver that goes to the track a few times a year it is a big upgrade for the buck.

[flewis763]

Reason why I ask is I have the XYZ BBK on the front and I think the bias is just +2%. I might be interested in the rears, how close are you to getting enough people to make a run?

I would like to start machining next week. I have had a few guys that want just the rear because they already have the fronts done with other kits too. besides the braking increase, you also have a cooling increase do to the increase in surface area per revolution. that will help eliminate fade on the track quite a bit.

[green-lantern]

you also have a cooling increase do to the increase in surface area per revolution. that will help eliminate fade on the track quite a bit.

Honestly to me this seems like it's main advantage with this kit, and mainly what I'm interested in. I'll probably have to do some digging before I commit. I'd like to get a better idea what the bias would be.

Thanks

[flewis763]

Honestly to me this seems like it's main advantage with this kit, and mainly what I'm interested in. I'll probably have to do some digging before I commit. I'd like to get a better idea what the bias would be.

Thanks

what size are you running up front now, 356mm?

[flewis763]

also for some more pics of the rotors side by side and on top of each other here ya go. these are with 2g rotors.

[sergechronos]

I'll throw a few of my own in here, this is against 1G fronts and rears

[flewis763]

I'll throw a few of my own in here, this is against 1G fronts and rears

cts v calipers are the next thing I am working on using the same rotor. it will be more of a track upgrade. idk how soon ill get to it though. I still need to order the calipers.