HiCustomerthis is lostrider, hope you didn't put too much pressure on the calipers with the C-clamp, these pistons screw in to retract them, there is a special tool to do this with, you can purchase it at most parts stores, the one in the diagram may differ from what you may find, but there is the procedure, hope this helps.
NOTE: Make sure the caliper piston boot is clean and free of foreign material.
NOTE: Position the notch in the caliper piston so that it will correctly align with the pin on the backside of the inboard brake pad.
...Thanks LostRider. This is the first time I ever ran into a problem like this, doing brakes. Who would of thought of 'screwing' in the brake caliper. Live and learn!