Investigation of brake squeal and the influence of the abutment faces

This paper demonstrates the influence of the trailing end of the piston, or inboard, pad on the propensity of a brake to generate audible squeal. The unique technique was employed to measure the dynamic centre of pressure at the pad/disc interface during a normal braking operation. This novel technique uses an embedded pressure sensitive film within the pad. The paper also presents the co-planar analysis of the pad/caliper contact regions and its influence on the position of the disk/pad “Centre of Pressure” (CoP). The analysis shows how the trailing end of the piston pad influences the position of the CoP and goes on to explain why the centre moves as the pad abutment vibrates against the abutment. The paper includes additional work with a 12 piston opposed caliper where the initial CoP may be varied both along the pad and radially. Results show a very definite movement of the centre of pressure as the brake pressure is increased.