2001 1150 GS, 37,400 mi. I was following the rear brake pad replacement manual from the hall of wisdom and everything was going well. I was taking advantage of a rear tire renewal and I only wanted to disassemble and lubricate the rear caliper assembly and inspect the pads. I separated the carrier and caliper but when I went to push back both pistons with a block of wood they wouldn't move. I didn't have a small c-clamp, tried a larger one which really could not get a centered purchase on one of the pistons, and then figured, no problem, when I reinstall I will use the hydraulic brake system pressure to get them moving. But after I remounted the caliper, the pistons would not budge. When I pumped the pedal the (original rubber) brake line bulged just above the banjo crimp, which looked a little ominous but I was getting pressure. Brake worked fine before I disassembled. I didn't touch the foot brake while I did the work. The pistons are equally showing about 5/16" out of the caliper. Wondering what I try next: more c-clamp pressure, disassemble and rebuild caliper, and how the hell did I screw this up?