Originally Posted by Island_370

If you notice this......before you run out and buy a $$$$ brake kit.....

Most of the knockback is a result of hub/bearing flex not the caliper. As the car loads and the parts flex, the angle of the rotor in the caliper deflects from 0 degrees (vertical) and pushes on the pad causing the pistons to retract. When the car unloads and the rotor returns to 0, there is now extra clearance. The seal design on the caliper pistons can help this, but piston springs are really the only fix----aside from rebuilding the suspension/hub with unobtainium.

Piston springs are for track only cars. the pads will overheat on the street and wear REALLY fast.

I have not yet had the Z on the track, but my Audi did it with aftermarket calipers (Alcon 6 pots--very good calipers). I was able to adapt by learning to use my left foot on brake. I would gently---GENTLY--tap the breaks on a straight before a big braking zone. It brought the pistons back and put a bit heat into the pads. Gave great initial bite. It is a learned skill to give just enough pressure to set the pads, but not enough to add too much drag. A series of light taps (~5-8) worked best for me.