I was able to remove the actual brake pads from the rear but I am unable to depress the piston that holds the pads on. I used a C-Clamp but that is not working. I also tried loosening the bleeder valve and it still would not go in. I can not get the pads on unless the piston goes in. Is there a key to doing this. Do I need to loosen any bolts or anything. ANy suggestions would be greatly appreciated. Thank You