Took my '98 540i to the indy to install Brembo oem rotors and Hawk HPS pads. He ended up reinstallig the old rotors for now because when he drove it to bed the pads he said "they were jumping and banging all over the place". He took it apart again and the calipers,pads, and rotors all looked ok. Yesterday it happened one time while driving at low speed-scared the hell out of me! His desciption is accurate.It was kind of like when you have no throttle and release the clutch,but faster 'bucking'.Note that this is an auto trans and the clutch reference is only to describe. Help?