[Ron Sutton]

Hey Josh,

Originally Posted by BANKO

Ron, thanks for the charts! I've been studying and pondering many questions. It is great to see a line up of all the calipers. Interesting that the GM single piston on and 11.88" rotors have almost as much clamping force as the Wilwood massive TC6R.
That's what fools a lot of car guys. You see all those pistons & think the math adds up but it often does not. The formula for piston area (or area of any circle) is Radius x Radius x Pi. Remember radius is half of diameter.

So a stock GM Camaro, Impala or C10 pick up caliper from the 70's has a piston size is 2.9375. Divide by 2 for radius = 1.46875.

1.46875 x 1.46875 x 3.1416 = 6.777 inches of piston area. Times 2 calipers on the front = 13.55 total piston area for the front.

The PBR/Z06 Caliper has 6 pistons, but you only account for one side, so 3 all the same size at 1.30". When you run the braking formula, you end up with 7.964 total piston area for the front.

There isn't anything wrong with these PBR/Z06 calipers. The Z06 system was designed with larger rotors, higher CoF brake pads & more pedal ratio than the Camaro, Impala or C10 pick up. I'm not sure if the M/C size if different. But when you're swapping a brake system into a car, you need to account for these details in the total system.

Important Note: I'm not sure if I read this correctly or incorrectly ... but if you have the proportioning valve all the way "out" ... that should reduce the rear brake force by 57% ... and is reducing your total braking force.

If that is correct ... you need to start by opening it up to restore rear braking force ... and then go test your brakes in a safe place & see how it does. If you get it where it's locking the rear brakes up ... reduce the rear braking force just to the point it doesn't lock up the rears ... and let's see if that's better.


Can this TC6R caliper be used on a 13" rotor, the smallest size rotor i saw offered is 16", reading the caliper drawing shows it may accomodate a 14" rotor.
I do not know, as I have not worked with this caliper. It was designed by Wilwood to be a street caliper for pickups & SUVs. That's outside my wheelhouse.

With a 16" shouldn't this lead to a dramatic brake torque increase?
You don't need 16" rotors. I have designed brake systems with 5500# total braking torque utilizing 11-3/4" rotors front & rear. The main reason to increase rotor size is to increase the thermal capacity of the rotors to survive long races.

I never run a rotor larger than needed, because the rotational weight KILLS performance. It adds to unsprung weight ... making the suspensions job of controlling that wheel harder. And it adds to the rotating weight. Not only is the rotor heavier ... but you're moving it out on a bigger radius.

I cringe when I see guys spend $1200 a wheel to shave 2-4# off ... then add rotors that weigh 6-8# more.

I learned long ago, if we cool the rotor properly, we can run a little less mass in the rotor ... so it's lighter. For this advantage ... I make cooling the rotors a priority.




This got me thinking it might be an alternative to the W6A (5.4) on a 14" rotor since it provides 6.9 piston area!!! Key downside is the availability for more tack oriented pads, looks like the highest CoF is .40, comparable to the HP+ pads.
The W6A is a real race caliper with a wide variety of pads available ... including race track compounds. The TC6R is a street caliper with a lot of piston area ... but a narrow selection of street pad compounds.


I was also thinking of the benefits of adapting the GM single piston caliper to a larger rotor. Not very sexy, but effective. Quite disappointing to see the Z06 6 pistons have such low clamping force.

Again, nothing wrong with the PBR/Z06 caliper. I think your application may need more aggressive pads & more rear braking force to be a good system. Also nothing wrong with upgrading it as you've mentioned doing.

Please go test the proportioning valve adjustment to confirm that is not a part of the problem.