Influence of Surface Modifications on Vehicle Disc Brake Squeal

Squeal from brakes is a problem in the automotive industry and large efforts are made to understand the squeal tendencies. The approach taken is mainly to change the design of the caliper, fine-tune the brake pad material and finally to trim the introducing shims on the backside of the pads. Despite these efforts still no general solutions exist. To advance the situation, a deeper understanding of the actual source of excitation of the sound in the friction interface is needed. However, in the present investigation the surfaces modifications of brake disc and pad have been tested with respect to the understanding properties. The surfaces modifications are slotted pad material and coated disc. All tests have been made in a brake test stand consisting of a complete front wheel corner of a vehicle. The changes have resulted in a significant understand of the generated noise. This is due to the changing of the coefficient of friction between the disc and pads which has a strong influence on the squeal propensity.