|
|
surfaces can be restored by machining in a disc brake Replace the rotor under the following conditions: • Tapered • Hard Spots • Cracked • Below Minimum Thickness ROTOR MINIMUM THICKNESS Measure rotor thickness at the center of the brake shoe contact surface. Replace the rotor if worn below Rotor minimum thickness is usually specified on the rotor hub. The specification is either stamped or ROTOR RUNOUT Check rotor lateral runout with dial indicator C-3339 (Fig. 52). Excessive lateral runout will cause NOTE: Be sure wheel bearing has zero end play Maximum allowable rotor runout is 0.102 mm (0.004 in.). ROTOR THICKNESS VARIATION Variations in rotor thickness will cause pedal pul- sation, noise and shudder. Measure rotor thickness at 6-to-12 points around the rotor face (Fig. 53). Position the micrometer approximately 25.4 mm ( 1 in.) from the rotor outer circumference for each mea- Thickness should not vary by more than 0.013 mm (0.0005 in.) from point-to-point on the rotor. Machine DIAGNOSIS AND TESTING - BRAKE DRUM IN The maximum allowable diameter of the drum braking surface is indicated on the drum outer edge. BRAKE DRUM RUNOUT Measure drum diameter and runout with an accu- rate gauge. The most accurate method of measure- Machine the drum if runout or variation exceed values. Replace the drum in hat rotor if machining STANDARD PROCEDURE STANDARD PROCEDURE - DISC ROTOR The disc brake rotor can be machined if scored or worn. The lathe must machine both sides of the rotor Fig. 52 Checking Rotor Runout And Thickness Variation 1 - DIAL INDICATOR Fig. 53 Measuring Rotor Thickness 1 - MICROMETER TJ BRAKES - BASE 5 - 29 ROTORS (Continued) |