Disc Brakes - Noise Explanation

Bulletin No. T 87-47
File in Group 5
Number 16
Corp. Ref. No. 715001
Date Dec. '86

SUBJECT: DISC BRAKE NOISE

MODELS AFFECTED: ALL WITH DISC BRAKES

In recent years, disc brake lining materials on most Cadillac models have been changed from an asbestos material to a semi-metallic friction compound. These changes have been made for improved brake system performance and to reduce the use of asbestos materials.

Each vehicle brake system is designed and validated using a particular lining material in order to meet stringent Federal Motor Vehicle Safety Standards. When servicing any brake system, it is important to use only the specified lining material for replacement purposes. Use of nonapproved lining material may result in improper front-to-rear brake balance, increased fade and degraded braking performance.

Semi-metallic brake linings demonstrate certain advantages over asbestos materials, especially in the area of fade resistance. Semi-metallic linings, however, are sometimes more abrasive than asbestos and as a result may create additional noise and faster rotor wear.

A certain amount of noise is inherent in any disc brake system which uses semi-metallic lining materials. This noise may be heard as a high-pitched squeak or squeal which occurs during light to moderate brake applications. In most cases this noise should be considered normal.

Other brake system noises, however, should not be considered normal and should be diagnosed as described in Section 5 of the Service Information Manual. All disc brake systems are equipped with a lining wear indicator which creates a loud, high pitched squeal while driving with worn brake linings. This noise normally occurs when the brakes are not applied. Refer to Section 5 of the appropriate Service Information Manual for more information on lining wear indicators.

If the brake system is functioning normally and it is the judgement of the dealership service department that the demonstrated level of brake noise is normal, this should be discussed with the customer and no repair should be attempted. Efforts to eliminate normal brake noise are often effective for only a short period of time.