I'm changing my rear rotors and pads on my 97 Cobra and for the life of me can't get either rear caliper back on. The caliper is hitting the pads. I've triple checked my parts to make sure they are correct and they are. I've retracted the pistons as far back as they will go and still they won't fit. Any ideas would be greatly appreciated. Is it possible the pistons aren't retracted all they way? I removed the cap to the brake reservoir to relieve any pressure. Thanks.