Abstract
Keywords: Noise, pressure, spragging.
Pressure sensitive film embedded into the body of a pad friction compound is a unique technique used to measure the dynamic centre of pressure at the pad/disc interface during a normal braking operation. This paper presents the co-planar analysis of the pad/caliper contact regions and its influence on the position of the disc/pad centre of pressure. The measurements, using the embedded film, show the centre of pressure to move considerably both along the pad and radially during a light braking application but the movement is less as the pressure increases. In addition it is shown that disc speed has little effect on the centre of pressure regardless of pressure. The analysis shows how the trailing end of the piston pad influences the position of the centre of pressure and goes on to explain why the centre moves as the pad abutment vibrates against the abutment. Pad wear measurements complement the collective information. The results may be related back to the mounting geometry of the caliper, or carrier bracket, which is subsequently compared to the effective "spragging angle". The paper includes additional work with a 12 piston opposed caliper where the initial centre of pressure may be varied both along the pad and radially. Results show a very definite movement of the centre of pressure as the brake pressure is increased. The results also show little influence on the position as disc speed in increased.