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This paper summarizes a case study involving the characterization and reduction of the brake noise on the 1998 Mercedes-Benz M-Class Sport Utility Vehicle. Noise was identified on both the front and rear brake systems. The front disc brake noise was described as a low frequency squeal, while the rear disc brakes exhibited a high frequency squeal. Investigation into this problem incorporated vehicle and dynamometer testing as well as experimental modal analysis (EMA) for component characterization. The use of EMA and dynamometer testing resulted in the identification of several possible countermeasures including: pad chamfers, pad compressibility control, pad scorching, and rotor modifications. Various noise insulators were also examined as a potential solution to this problem without making any additional changes to the existing components. Dynamometer and vehicle testing were used in the evaluation and selection of a noise countermeasure for each the front and rear braking systems.

Noise and vibration related functional characteristics of the disc brake has, for a long time, been the nemesis of the design engineer's existence. New methods of measurement and analysis techniques are providing information which improves the practical assessment of a disc brake design and improves the basic understanding of noise and vibration operational aspects. Utilization of these new techniques make undesirable roughness prediction more feasible and potential solutions more rapidly identifiable. Development of these new measurement methods involved the measurement of in-stop torque variation and rotor thickness variation (TV), as well as rotor total indicated runout. Detailed analysis of the torque variation signature of vehicle and dynamometer data indicates significant differences. These differences are shown to be influenced by vehicle suspension resonant characteristics and (in-stop) changes to both lining and rotor mechanical characteristics.