Subaru Enthusiasts Car Club of the Sierras - View Single Post

GarySheehan · 2004-02-22, 06:50 PM

Dean,

The WRX has two 42.5mm pistons in the caliper. The Stoptech caliper uses one 36mm piston and one 40mm piston. You do not factor in all four pistons in the area, only two. This is because the two piston floating stock caliper applies the same force to both sides of the rotor (i.e.-a 2 piston floating caliper equals a 4 piston solid mount caliper with equal piston sizes).

All of your references to the differential in temperature across the pad is because the trailing edge of the pad is impeded by the debris and outgassing. More force is required at the trailing edge to force it through the debris.

In discussing the fast way around the track, you are correct, there are instances where you do not brake at the maximum because of balance of the car, etc. But our entire discussion to this point has been discussing maximum braking ability of a system. So, in all of the major braking zones where the intent is to scrub off a significant amount of speed, I use the brakes to the maximum of the tire's ability. Standing on it's nose. As I transfer straight line braking for turning, I am still braking at the limit of the tire just prior to lock-up.

Very short braking areas where there is only a little bit of speed to scrub, you don't hit the brakes to the point to upset the car. But you wouldn't be utilizing ABS to have the car stand on it's nose as you described either.

Take Sears Point. There are six "stand the car on it's nose" braking zones and only two places where you do not brake at absolute maximum, because you don't need to shed that much speed.

You didn't mention anything about the majority of the discussion revolving around how the tire traction breaks away quite a long time before wheel lock-up. That was actually the most important topic in this thread. Did you understand what I was trying to convey?

Gary
Sheehan Motor Racing
www.teamSMR.com

2004-02-22, 06:50 PM	#136
GarySheehan EJ22 Join Date: Aug 2003 Posts: 172 Never let the driver work on the car...	Dean, The WRX has two 42.5mm pistons in the caliper. The Stoptech caliper uses one 36mm piston and one 40mm piston. You do not factor in all four pistons in the area, only two. This is because the two piston floating stock caliper applies the same force to both sides of the rotor (i.e.-a 2 piston floating caliper equals a 4 piston solid mount caliper with equal piston sizes). All of your references to the differential in temperature across the pad is because the trailing edge of the pad is impeded by the debris and outgassing. More force is required at the trailing edge to force it through the debris. In discussing the fast way around the track, you are correct, there are instances where you do not brake at the maximum because of balance of the car, etc. But our entire discussion to this point has been discussing maximum braking ability of a system. So, in all of the major braking zones where the intent is to scrub off a significant amount of speed, I use the brakes to the maximum of the tire's ability. Standing on it's nose. As I transfer straight line braking for turning, I am still braking at the limit of the tire just prior to lock-up. Very short braking areas where there is only a little bit of speed to scrub, you don't hit the brakes to the point to upset the car. But you wouldn't be utilizing ABS to have the car stand on it's nose as you described either. Take Sears Point. There are six "stand the car on it's nose" braking zones and only two places where you do not brake at absolute maximum, because you don't need to shed that much speed. You didn't mention anything about the majority of the discussion revolving around how the tire traction breaks away quite a long time before wheel lock-up. That was actually the most important topic in this thread. Did you understand what I was trying to convey? Gary Sheehan Motor Racing www.teamSMR.com