Surface characterisation of brake pads after running under silent and squealing conditions

Despite many investigations over the years to clarify the mechanisms causing automotive brake squeal the phenomenon is not yet fully understood. This paper focuses on the previously almost unexplored area of the connection between brake pad surface topography and the occurrence of squeals. Two sets of brake pads were subjected to brake tests in a special test rig. Both pads are of a metal-fibre reinforced organic type, the first being a standard production formulation while the other is slightly reformulated for increased high-speed performance. Characterisation of the brake pad surfaces was performed after interrupting the testing under both silent and squealing conditions. By comparing these pads, the correlations between squealing and the number of contact plateaus, their size and the total contact area were investigated.