You can find out if it's pressure or mechanical (stuck piston) by releasing the bleeder valve. Get it hot and bound up, jack up the corner, spin the tire to verify it can't easily turn, then crack the bleeder and see if the tire spins better. I'd bet that would do nothing and it's a bad caliper.

 

Well I tore it apart yesterday. I noticed that after I ground grooves out of guide rails it brought the pads closer to the center of the rotor. It looked like the metal part of outside pad was rubbing the part of the rotor that goes over the hub. I ground the metal part of the pad back a little. Drove it to work last night (about 20 miles on the highway doing 65). Both rims felt about the same reached back and grabbed the caliper itself and it was cool. So I'm wondering if this whole time it wasn't the brakes dragging causing all this. It was the metal part of pad rubbing the rotor. It didn't rub enough to cut into anything, but enough to make it shiney.