I bought a car a few months ago and I have been having this never ending saga of things that just dont match up. So the brakes are **** and I decide to get new pads tonite. The guy I bought it from said the brakes are from a 98-01 Integra discs... I go buy 98 integra pads... I get everything off, etc.. lining up the new pads, looks good, go to put the rest of the caliper back on and... the pads + rotor = too big for the caliper to fit over the top of them. Could this just be warped rotors? If I put the old **** brakes back in, they are worn far enough that it looks fine. The cylinder on the caliper which I believe is the piston wont retract, etc.. I have only changed pads on the rear of my last si and that piston retracted. This is just basically a cup back there and nothing inside of it but some rust.

WTF?

 

you have to get something to clamp the caliper and push the piston back into the caliper. Use a big pair or channel locks. It should be farily tough to squeeze back in.
PS: make sure the boot around the the piston is seated properly!!!