Aspects of Disc Brake Judder

Abstract

Brake judder is a braking induced, forced vibration occurring in different types of vehicles. The judder frequency is directly proportional to the revolution speed of the wheel and therefore also to the velocity of the vehicle. The driver experiences judder as vibrations in the steering wheel, brake pedal and floor. In the higher frequency range, the structural vibrations are accompanied by a sound. Brake judder primarily affects the comfort but could, when confronting an inexperienced driver for the first time, lead to faulty reactions and reduced driving safety. Furthermore, a specific type of judder, so-called hot judder, is related to disc cracking. There are numerous publications available dealing with high frequency vibrations, such as brake squeal, including mathematical models for analysis and simulation. However, low frequency phenomena, such as brake judder and groan, have received much less attention. There is a growing interest from the automotive industry concerning brake judder. Even though few companies would admit that they have the problem, it is not unusual to meet people who have experienced the problem in their own passenger cars. Much of the knowledge concerning brake judder remains within the companies. Hence, very few people have the full picture. The purpose of the present paper is to give an overview of the brake judder problem.