The Measurement and Analysis of the Disc/Pad Interface Dynamic Centre of Pressure and its Influence on Brake Noise.

This paper discusses the measurement of the dynamic centre of pressure (CoP) of a brake pad during a normal braking event using a modified 12-piston opposed calliper. The modifications allow the centre of pressure to be controlled both radially and along the length of the pad, inducing a leading or trailing centre of pressure as desired. The technique is unique in its design and implementation. Both the centre of pressures of the in-board and out-board pads are recorded simultaneously with varying pressures and speeds. The results, which include pressure and force maps, show the position of the centre of pressure to vary considerably during a braking event, both radially and axially along the pad. The CoP offset is related to the calliper mounting geometry which is subsequently compared to the effective “spragging angle” and the generation of brake noise. It is seen that by inducing a leading offset noise may be generated and subsequently eliminated if a trailing centre is then induced. The results suggest that by careful selection of the backplate abutment friction level the CoP may be controlled to always fall within the “stable envelope” region and so resist noise generation.