Changed rear rotors and brake pads, now the calipers wont squeeze when brakes are pushed. Do the pistons on 2008 jeep wrangler need to be turned to be pushed in or can they be pushed in with a c clamp?

Check the MECHANICAL (parking) brake shoes BEHIND / or on the inside of the rotor of the rear wheel in question.

If the piston isn't coming out on the caliper to allow the pads to squeeze the rotor - that make explain why the pads / rotor look good - they're probably not being used.

brakes are brakes, push in , turn in, or two piece calipers. remove wheel , remove two bolts that hold caliper in place, remove replace pads if rotors look good if not remove caliper retainer and rotor replace or have resurfaced at local part store with service. if push in piston push in with c-clamp or piston tool, if turn in will be solid on top with slots for tool to turn in turn to right, tool can be gotten at parts store, if two piece take apart and put back then bleed brakes.

You will have to use a c-clamp or brake piston compressing tool to get that piston back in, while you have the brake master cylinder fluid reservoir cap off.

When you say replace,I assume you mean brake pads
Calipers last for years
You have to turn the piston in first,that is later ratcheted up, for parking brake initial setting
Then you need to push the piston into the caliper,works best if you open the bleeder valve
You will be bleeding all four calipers every two years anyway.
You may be able to get a tool for turning the rear piston or modify one as I had to since none were avail for a Lincoln LS
Have the rear rotors turned,don't put new pads on a worn rotor

The rear calipers on these models require a special tool that compresses and turns the piston in at the same time -- most parts stores carry this tool.

It is called a caliper piston press -- and it installs where the pads would go and acts like a c-clamp,when turning handle it will turn the caliper piston backinto the caliper as it compresses it.
Anytime the brake rotor or brake pads are being replaced, the rear caliper piston must be seated (bottomed) to compensate for the new brake rotor or lining. Because the Parking Brake self-adjuster mechanism is attached to the piston, a special seating method is required. The only acceptable method is by rotating the piston back into the bore using Retractor,MILLER Special Tool 8807, . Any other seating method will damage the self-adjuster mechanism.
Good luck and hope this helps.

The problem lays with the Caliper itself and/or the brake hose connected to the Caliper.
However if you replaced the pads, did you also replace the Rotors or have them Turned? The old pads wear the rotor. New pads on old rotors that have not been replaced or turned may end with rubbing or stuck brakes.
A simple way to test whether it's one and/or the other:
1. Remove the Caliper from the rotor, remove the pads. Keep for now the caliper attached to the brake hose.
2. Very slowly push on the brake, exposing more of the piston out of the bore. Not all the way. Usually until the rubber dust seal/boot is fully extended.
3. Check the seal/boot for cracks and tears, and if clean or not. Bad seals may prevent the piston from re-seating.
4. Using a c-clamp and pushing straight in: Try repushing the Caliper Piston back into the Caliper Bore (the cup back into the hole). It should go back in realitively easy.
5. If it doesn't go back in easy: Again slowly pump the brake and re-push the pistons back out to full extended seal/boot (but not the piston out of the bore).
6. Detached the brake hose from the caliper.
7. Again using a c-clamp and pushing straight in: Try again to repush the caliper piston back into the bore without the hose attached. If it goes back-in relatively easy - the caliper is okay...it is the brake hose.
8. If the caliper piston does not go back in easily - Replace the caliper.
9. When Installing the new (reman) caliper, remember to bleed the brakes.
TRY EITHER OR #10 OR #11 BELOW:
After the new Caliper is reattached to hose and has been bled:
10. Again push on the brake petal to fully extend the caliper piston fully (rubber seal/boot fully extended) Again do not push the piston out of the bore! Try pushing the piston back into the bore. If it does not re-seat relatively easy: Replace the brake hose.
11. Another method: After replacing the new caliper back on the rotor: Assumng the entire front end (2WD front wheel drive) or entire vehicle (2WD rear wheel drive) or (4WD all the time) is jacked up off the ground
a. Put the lug nuts back on the rotor.
b. Have helper Start the vehicle and place in Drive. Don't step on gas!
c. Have then let off the brake and then engage the brake.
d. When they let off the brake watch to see if the Rotor is turning or not, if rubbing or not. Or if still sticking.
e. With a new caliper, turned or new rotors, and still a problem? It is the brake hose!
12. Replace the brake hose and try again.

Another method but more expensive:
OR Replace the calipers, brake hoses; bleed and test!

If this helped or not; or if you need additional help or have addtional questions let me know on fixya.com!

Parking brake is operated by a cable and not the caliper. Your car has disc brake pads for squeezing the rotor to stop, the parking brake has drum type brake shoes that push out on the inside of the rotor. Changing the disc pads only requires squeezing the piston back in like usual.

Squeeze the pistons with large pliere to get a little more clearance

You will need a 7mm allen wrench or socket the socket is easier with a ratchet to undo the 2 bolts that hold the caliper on.After you take the bolts out take a screw driver and pry up on the caliper to release it off the rotor. your calipers are on top of the rotors. To compress the caliper pistons in take a pair of channel locks that open up alot then with the back brake pad still on squeeze the piston and pad in. That should do it :)

All you have to do is take off your calipers and the rotor will slide right off. Use a C clamp to push the piston of the caliper back in so you can put your new brakes on.