The best way to spread the pistons to get the new pads to slide over the rotor is while you have your old pads still in the caliper, wedge them apart with a screwdriver. Try to get them as far apart as possible, which will make it a breeze to just slide them over the rotor with the new pads in. DO NOT PRY APART THE PISTONS WITH THE NEW PADS! You will damage the new pads and hurt their longevity.

 

If I can recollect from my Cherokee Front Brake Paddays, I would remove the caliper, pads, then place a 3/4x4 or 2x4 block of woodagainst the piston, then place one end of the c-clamp on the caliper external housing and the other end on the outside of the wood, and retract the piston from there. Once the piston was retracted, I would place the inboard pad on first, then the outboard pad slide over the rotors, torque the bolts and presto done. Another option was place the c-clamp against the piston and retract like Chris said, using the old calipers since they are going to be turned in for the core anyway. I agree, don't use the new pads to retract the piston, no sense risking any damage to the good stuff right?I would say no larger than 2x4, anything larger there might not be enough room to fully retract the piston, and much less than a 3/4x4 it might be too brittle and break when tightening.

 

Update, It got above 7 degrees F yesterday and today, So true to my word, I got the inspection done. As suspected, Front and Rear Pads/Rotorsneed replacing, although Ibelieve I might be able to swing a little longer on the rear rotors. Next week weather permitting I will complete the tasks.