I actually bought that little tool that you add to the rachet to make it turn. I tried to loosen the nipple and it didn't help any. It is possible that the piston is locked/frozen up but then it would be unusual for both rear calipers to be locked up. One side was considerably more worn then the other (one to the metal). I'm not sure how much pressure i should be putting on it as i'm screwing it in. It just turns and doesn't move.
