Article 3244 - Disc Brake Rotor Refinishing Tools

TSB #157 - January 22, 1971
(All Passenger cars - 1968-71)

A new disc brake rotor refinishing micrometer gauge bar and ball tool (Tool T-71P-1102-A) has been developed to determine maximum stock removal from the inner braking surface of disc brake rotors. (Refer to TSB No. 151, Article No. 3110, October 30, 1970.)

This article explains the use of Gauge Bar and Ball Tool T-71P-1102-A.

Maximum allowable stock removal from the inner rotor braking surface is determined as follows:

1. Remove the hub and rotor assembly from the car.
2. Remove the inner grease retainer and bearing assembly from the hub and rotor assembly. Thoroughly clean the inner bearing cup and hub bore.
3. Carefully place the gauge ball in the inner bearing cup (do not drop).
4. Set the micrometer of the gauge bar to the dimension for the car model rotor being measured (Figure 1 ). This dimension allows for maximum stock removal.
5. Position the micrometer gauge bar on the rotor inner braking surface with the micrometer centered over the ball (Figure 2 ). Measure the distance between the micrometer base-line setting (step 4) and the ball by turning the micrometer down to touch the top of the ball and calculating the difference between that reading and the original setting. This distance is equal to the maximum allowable stock removal from the inside braking surface only. If the micrometer end, at the base-line setting, touches the ball, no additional stock removal is allowed. If the micrometer must be retracted from the base-line setting to allow the legs to set on the rotor surface, the rotor has had more than allowable stock removed and the rotor assembly must be replaced.

If the rotor thickness before or after re-finishing is less than the minimum shown in Figure 2 , the rotor must be replaced, regardless of the gauge bar and ball measurement.

Figure 1

Figure 2