Brake Noise and Judder

This chapter describes the causes, characteristics and possible solutions to automotive brake noise and judder problems with a review of published research in the field. It explains that brake noise is independent of speed, can occur over a wide frequency range, and can be fugitive, intermittent and variable in frequency and intensity. In comparison brake judder is a mechanical instability with a frequency related directly to rotor speed. Most brake noise is caused by frictionally induced dynamic instabilities in the brake (‘source’), which create vibrations of brake components that then radiate the sound (‘response’). Experimental and analytical approaches to investigating the mechanisms and characteristics of brake noise and judder are discussed, and ‘best practice’ design rules to minimise brake noise and judder propensity are suggested. Modal and geometric coupling is shown to be important, and computational methods for frequency domain instability analysis using eigenvalue extraction are compared with time domain multi-body dynamic analyses.