Preventing Disc Brake Squeal Using a Thin Plate Shim

Squealing from car disc brakes is a source of considerable discomfort and leads to customer dissatisfaction. The high frequency squeal noise above 1 kHz is very annoying and difficult to eliminate. Good braking performance against noise is considered to be a big market advantage. Reduction of brake squeal in the design stage is a formidable challenge that is faced by the automotive engineers. This paper attempts to provide a solution of eliminating disc brake squeal up to 10 kHz using a thin plate shim. First squeal occurrences in a disc brake assembly without thin plate shim are investigated for various operating conditions using a drag type brake dynamometer. Having identified the dominant squeal frequencies several shapes of thin plate shim are proposed and tested. The aim of using thin plate shims is to modify contact pressure distribution on the brake pads. A good shim should be able to effectively suppress and prevent those squeal frequencies generated in a disc brake system.