Changing Rear Brake Pads on 2007 G6

Ok, I've changed brake pads on GM Cars, Trucks and SUV's and have never had difficulty compressing the brake caliper piston to enable installing new pads. After several attempts using a Disck Brake pad spreader, I gave up. Is it necessary to open the bleeder valve on rear calipers to compress the piston ?

You need a caliper spreader that also turns the piston as it is compressed into the caliper since the rear calipers function as the park brake. The park brake actuator is threaded into the piston. When you apply the park brake the actuator turns and since the piston is keyed to the inner brake pad this causes the piston to extend rather than turn also and apply the brakes. The cube compressors are the cheapest. Just drive the piston into the caliper with a 3/8" extension and ratchet and push as you do it.
http://t0.gstatic.com/images?q=tbn:ANd9GcSpSooEHBZ06AYoFMXMaEZMNzQK-sz1K375dM_2F6JyEYM9l6ph
Sent from my Droid X. Typos probable.

Thank you very much for the information. I'll get one of the cube compressors and finish the job ! Thanks again for your help, it is appreciated.

You're Welcome. Glad I could help.

Sent from my Droid X. Typos probable.

Man, they have been doing that since the late 80's , on "W" cars....remember the C-clamp tool with the special fitting on the end, that was needed to depress the piston?