The effect of reduced contact area on the occurrence of disc brake squeals for an automotive brake pad

Three sets of brake pads were subjected to a series of squeal tests. The pad area in contact with the brake disc was successively reduced down to 50 per cent of the original by removal of friction material either at the leading and trailing edges, at the outer and inner edges or spotwise removal of interior area by drilling. The pad surface geometry strongly affected the occurrence of brake squeals, with a significant reduction for all three pads with 50 per cent contact area. However, the average squeal noise level seems to be controlled by the pad contact length in the sliding direction.