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"r.:;V- ' ' '9 BRAKEUNER SCHOOL BUS TECHNICAL BULLETINS -t(h`X An 1C Industries Company Bulletin No. 3 Friction Products Division, 3001 W. Big Beaver Rd.. Troy, Michigan 48084-3184 Brake Noise Acceptable brake performance after brake reline is dependent upon how well the brake system was inspected and the quality of maintenance performed Efficient brake operation requires every component in the system to be in good working condition. Lining to Drum 1 Contact Check all used brake shoes for being bent and/or stretched. Shoe table must be Hat to within .002 inch per 1 inch of table w>dth. Measure shoe. Compare dimension "X" to that of new shoe, if difference is greater than 1/64", discard shoe. 2 Machine Disc Rotors and Brake Drums for concentricity with spindle and axle. Machining disc rotors and drums may remove heat checks and blue spots, but they will reappear later. As a result of heat input from brak ing. it is best to replace severely heat checked and blue spotted rotors or drums during reline. Remember, replace rotors or drums in pairs. It Is suggested that new drums also be machined on their hub to minimize runout. One of the most common complaints on school buses is brake noise. Brake noise is usually the rbsult of inconsistencies in the brake system. Some factors affecting brake noise are as follows: Use Oversize Lining 3 when drum diameter will accept it There should be 005-.010 inch clearance be tween lining and drum at points A and B. Center contact is desirable for smooth braking. To insure optimum lining ana drum life, each brake must do its share of tne braking. Improper lining and drum con tact will result in wheels with good contact to be over worked, resulting in abused lining and drums/rotors. Brake Hardware 4 Brake shoe hold down springs or clips and shoe return springs must be replaced at each reline. Return springs of varying tensions must be installed in their proper locations, A-1003 2/85 Ported in U S.A SCI 03103