Mazda Trucks 1994-1998 Repair Guide

Brake Drums

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REMOVAL & INSTALLATION



See Figures 1 and 2


CAUTION
Older brake pads or shoes may contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid.

  1. Raise the vehicle so that the wheel to be worked on is clear of the floor and install jackstands under the vehicle.
  2.  



Click image to see an enlarged view

Fig. Fig. 1: To remove the rear brake drum, first safely raise the rear of the vehicle and remove the wheel ...

  1. Remove the hub cap and the wheel/tire assembly. Remove the 3 retaining nuts and remove the brake drum. It may be necessary to back off the brake shoe adjustment in order to remove the brake drum. This is because the drum might be grooved or worn from being in service for an extended period of time.
  2.  



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Fig. Fig. 2: ... then grasp hold of the drum and pull it from the axle flange and brake shoes

  1. Before installing a new brake drum, be sure and remove any protective coating with carburetor degreaser.
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  3. Install the brake drum in the reverse order of removal and adjusts the brakes.
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INSPECTION



See Figure 3



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Fig. Fig. 3: Drum brake service limits. The maximum inside diameter is cast into the drum

After the brake drum has been removed from the vehicle, it should be inspected for run-out, severe scoring cracks, and the proper inside diameter.

Minor scores on a brake drum can be removed with fine emery cloth, provided that all grit is removed from the drum before it is installed on the vehicle.

A badly scored, rough, or out-of-round (run-out) drum can be ground or turned on a brake drum lathe. Do not remove any more material from the drum than is necessary to provide a smooth surface for the brake shoe to contact. The maximum diameter of the braking surface is shown on the inside of each brake drum. Brake drums that exceed the maximum braking surface diameter shown on the brake drum, either through wear or refinishing, must be replaced. This is because after the outside wall of the brake drum reaches a certain thickness (thinner than the original thickness) the drum loses its ability to dissipate the heat created by the friction between the brake drum and the brake shoes, when the brakes are applied. Also the brake drum will have more tendency to warp and/or crack.

The maximum braking surface diameter specification, which is shown on each drum, allows for a 0.060 in. (1.5mm) machining cut over the original nominal drum diameter plus 0.030 in. (0.76mm) additional wear before reaching the diameter where the drum must be discarded. Use a brake drum micrometer to measure the inside diameter of the brake drums.

 
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