ON retracting the REAR disc rotor piston, do you compress it back or do you have to screw it back to clear the new pads?

 

there is a tool to use to screw the adjuster back into the caliper piston

 

yep cheap tool, little square thing that fits on a socket wrench, has 6 sides for different vehicles all with different points that fit into the piston to screw it in
think less than $10 bucks @ your local autozone or advance auto

 

Harbor freight also has the more complete kit, which fits better and is less likely to booger up your piston.

However, 95% of the time, I just use the little cube. It's quicker and if you're careful it works just fine.

 

http://m.harborfreight.com/four-wheel-disc-brake-piston-tool-68972.html?utm_referrer=direct%2Fnot%20provided