I just use a pair of Channelock water pump pliers on the M5 calipers, as well as on all of our other cars. You might want to spray a little penetrating oil around the piston as it accumulates icky stuff which will impede its retraction.
Steve
00 M5
Last edited by TurboCarrera; 10th March 2008 at 23:26.
Reason: grammar and clarity