[Dangerous Doug]

I recently upgraded my brakes from GM (Camaro) brakes to SSBC A185S's, and the pedal is nice and firm. The Camaro brakes always felt a little mushy, and I thought I had air in the lines (even after pushing a ton of fluid through on bleeding). I had a mechanic check it out and he verifiied that the mushy brake sensation was common to the Camaro calipers, and that I had no air in my lines. The Camaro calipers have a single, large piston, wherein the SSBC's have dual smaller pistons. The net result is I push less fluid through to clamp them down.

This thread is right on. The spongy feel is coming from either too small of a master cylinder or too large of caliper pistons. I think a master cylinder replacement would be cheaper than replacing your calipers.

DD