I recently changed my rear brake pads and rotors on my 2002 Chevy
Silverado 4x4.  After changing them and pressing on the pedal the
rear calipers wont release and "drag" while driving down the road.  
Thus, causing the pads and rotors to get very hot.  Removed them
and reinstalled the old pads and rotors and everything is working ok.  
I can get the pistons (single piston caliper) to go back in using a
C-clamp.  I also changed the front pads and have had no trouble at
all with the front end. Any ideas?
Answer: The new rear pads and/or rotors could be slightly different
than what you have on there, or be completely wrong. Something is
causing the pad to hang up which in turn isn't letting the caliper back
off after a brake application. Did the new pads include hardware? If
so, you should always use what comes with the new parts. There
could also be a machining error or other mis-manufacturing step on
the parts you bought. Your best bet is to get genuine GM parts to
replace your old brakes. Make sure everything looks identical in size
and shape, and be sure to install the pads in their proper location.
Usually the wear indicator goes towards the inside, but always check
first and put it back the way it was.