Pontiac Repair: 99 grand prix rear brakes, caliper pistons, rear caliper

Question
I've got a 99 Grand Prix. I know I need a tool to turn the rear pistons back into the calipers, but I can't find any information anywhere about the diameter of my rear caliper's piston. I don't want to take the car apart until i have the tool in hand. do you know what size the piston is on the 99 grand prix? Where's the best place to buy the tool i need cheap?

Answer
Hi Cliff:

you don't need to turn the pstons back in  on that car. The parking brake system is NOT part of the claipers. It's a drum in hat design meaning the parking brake is a shoe inside the rotor and it has nothing to do with the caliper pistons. just press them is with a big C clamp or a big pair of channel locks. No special tool is required. Good luck :0