1997 Buick Riviera Calibar

If I understood correctly, you're trying to push the pistions back in your brake calipers so the can again be installed on your rotors. Usually, the old pistion-side pad can be held in place with a large pair of adjustable pliers and squeezed back into place. If you don't mind spending a little money, almost any auto supply store can get you a neat little tool that sandwiches between the piston and the outer caliper 'ears'. Then, with a turn of a wrench, the piston is pushed back into place. I recommend still using your old inner brake pad as a cushion to push on, though. This kit also is a must-need for the rear 'screw-type' pistons that need to be screwed in (obviously) instead of pushed in.