Fieldhouse, John D., Ashraf, Naveed, Talbot, Chris J., Pasquet, T., Franck, P. and Gabriel, R. (2006) Measurement of the dynamic center of pressure of a brake pad during a braking operation. SAE Technical Papers.

This paper discusses the analysis and measurement of the dynamic center of pressure of a brake pad during a normal braking event. The technique is unique in its design and implementation. The process is progressive whereby the interface static measurements are first taken and then dynamic testing is carried out under braking. Two different measurement systems are considered during the analysis with one used to measure the center of pressure. Both the in-board and out-board pads are measured for wear but the piston pad was selected for pressure measurements. Validation of the spragging process is undertaken on both test rigs and vehicle trials. Pad wear measurements complement the collective information. The results show the position of the center of pressure to vary considerably during a braking event, both radially and axially along the pad. The variable "instability envelope" is related to the caliper-mounting geometry which is subsequently compared to the effective "spragging angle" and the generation of brake noise. It is seen that by careful selection of the backplate abutment friction level the center of pressure may be controlled to always fall within the "stable envelope" region.