with a C clam , make sure the you use sameting to protec the piston
How do you compress the rear break caliper, pistons on a 2002 Sierra ?
Get a "U-clamp" that fits over the caliper and crank it down.
After you remove the tire and the pad the caliper has to be twisted to compress. Yo will not be able to compress using a C clamp. I can't remember if it is clock wise or counter clock wise.
the caliper bolts require a 3/8" Allen wrench. You can buy these as a socket at just about any parts store.
It must be at the top. HIGHEST POINT so the air will come out.
It takes a T55 Torx bit on the front calipers.
Chevy came up with the brilliant idea of turn in calipers a number of years back. Check the inside of the caliper piston cup. If you see a square depression in the center, it is a turn or twist in caliper. DO NOT try to compress it. You'll damage the caliper and increase your brake job costs. Chances are when a brake caliper wont compress it is the type that must be turned and compressed at the same time and requires a special tool that you can borrow from a local chain auto parts like Auto Zone. That was the case on my 96 Buick Riveria rear disk brakes.
Try 3/8 Allen key , or 15 mm wrench.
if it is the same as the 2004 then you would be looking for a 14mm or a 9/16 size
you need two special tools 1. A T60 torx bit to remove the caliper bolts 2. A caliper piston compressor two large c-clamps will work but compress evenly and SLOW
stay American Chevy suburban
122"