Sounds like a brake pad issue.. If you are not having problems on the street but then comes race time and you are losing some pedal.. What is the part # on the pad you have right now? You need to find pads that have a higher coefficient of friction when you get them hot when autocrossing or open tracking.. More than likely you have a BP10 or 20 which will fade after a couple of laps.. street pads..

What brake fluid are you running? I hope you are not running dot 5 silcone..

I have a car in the shop that is set up for open tracking with smaller rotors, calipers & tapper bearings & have never had the customer complain about losing pedal or pad knock back

Hey Gonzo,
I read your PM and was going to look into the pads before I replied. I'm pretty sure they are BP10's. I looked recently and checked them on Wilwoods site. They are street mild track pads. It's not the pads even though braking improves with heat. I can replicate it easily on the street by doing a slalom. The pedal engagment point drops 2-3 inches. I'm running Wilwood Dot 3 fluid.

I would try some 15E or 15B pads.. I would not run BP10s for agressive street driving or autocrossing.. I have tested all of Wilwood pads & these are the ones that have worked the best for me!

Don't rule out pads!

This has been going on too long! How much could the excessive body roll be contributing to the lateral load on the caliper?

How much would 1" smaller rotors reduce the knockback vs how much performance would you sacrifice?

Is front spindle deflection a contributing factor?

You've probably done numerous hours of searching and reading on the subject and already seen this but:
http://www.stoptech.com/tech_info/wp_knockback.shtml

One way to possibly isolate the issue would be to test with active knickback springs in the suspect calipers.

This has to be very frustrating after a couple years, numerous hours and dollars. :mad:

Todd check your set20 bearings, my play increased after mileage and abuse. I now consider them a racing wear item. And it was not bearing wear is was the axle sideloads that put wear on the bearing seal cup.

I think Todd has thrown just about everything at this issue....

Yep, the rear bearings have loosened up. I've even thrown some shims behind the races with no noticable change. I want to go floater but hear a certain someone may have a solution in the works. :lol: (not me)

I adapted these to work on my car, it’s not a kit but just some parts that I made work, I had to make my own brackets, knockback is gone and the car stops amazingly well.

Rick, thanks for sharing your idea. I'm just not sold on a smaller rear caliper as hard as we run these cars.

Todd I agree with you but this did eliminate the problem and overall my brake performance is way better then when i had the 4 piston rears, another problem with this small calliper is they dont make an aggresive pad for it.

I will continue to work on another setup involving a 6 piston caliper that i can convert to a floater, more like a floating bracket.