Noise Reduction of a Twin Calliper Disc Brake by Angular Positioning of the Callipers

A noisy disc brake vibrates in a wavelike manner with a diametral mode of vibration. The mode shape
exhibits antinodes with angular spacing of a specific size related to the noise frequency and mode order. The sizes of the antinodes vary slightly with brake pressure which causes a slight change in noise frequency. If the angular spacing of the callipers is arranged such that an integer of antinodes between the callipers is not possible then the disc is inhibited from vibrating in a given mode and noise at that frequency is prevented. The paper demonstrates that at particular angular settings of the callipers certain frequencies exist yet as the angular settings are changed the disc mode order and related frequency changes. It is shown that the frequencies can be related to the angular spacing between the callipers and the free mode angular spacing of the disc waveform antinodes. An analysis of the geometry allowed the brake noise frequency to be predicted for a certain angular setting of the callipers and specific angular settings to be predicted when the brake would be quiet. It is shown that this analysis was successfully applied in practice on the test rig and on the problematic vehicle. It is shown that the theory may be extended to single calliper brakes and adjustment of the pad/disc
interface geometry.