Influence of the Shim Contact Stiffness on Disc Brakes Squeal Noise

In order to reduce brake squeal noise shims are really common proposition, however, to define whether a shim is good or not to fix a specific problem, only two things are considered: damping and the noise results obtained in dynamometers tests. In this paper it is presented the importance of the contact stiffness between the baking plate and the piston or caliper on the squeal noise generation and how the shim contributes improve this factor. A method to measure this property is presented as well the results obtained using this method, correlating the contact stiffness of a non-painted, painted and shim applied backing plate. In the end, we are showing how the brake pressure may influence the shim contact stiffness and consequently the noise generation.