....another time I found the perfect sized pebble wedged in the casting behind the pad and catching up in the casting bore and pad back. It seemed like it would hold up the rear part of the caliper, I am not sure if it was the cause though I cleaned it out anyways. I wonder if the rubber piston surround could have an unseen cut or tear in it that could cause dirt or ice to jam things up if it packed it's way in there.