Just did mine this week. The bolt is a size 50 torx but they can strip. I used vice grips as tight as I could pull make them with two hands to break the bolt free then the torx to remove. Bolts are much easier to acess if you swing the piston and pads out of the way by removing the locater pin. If this is foreign to you I would advise that you purchase a Chiltons and look at the pictures. All will become clear. Last bit of advise, the pistons do not just push back into place. You need a tool to turn them back down to make room for the new pads. Good Luck.

-Rob- 1998 Black SVT #460 K&N Cone Filter Magnecor Wires Alpine CDA-7892, Alpine 5x7 (4), Kicker Comp 10VR with Rockford amp.