Important: Brake pulsation concerns are usually corrected by refinishing or replacing the front brake rotors.
Do NOT weld a cracked drum. REPLACE a cracked drum.Braking Surface Finish
Use fine emery cloth in order to polish light scoring of the drum braking surface less than 1.5 mm (0.060 in). Light scoring is not detrimental to brake system operation. Resurface or replace the brake drum if deep scoring in excess of 1.5 mm (0.060 in) exists. Deep scoring may cause premature brake lining wear and diminished brake system performance.
Inside Diameter
The brake drum has a DISCARD dimension cast into it. This dimension is NOT a maximum refinish dimension. Measure the brake drum inside diameter prior to refinishing the drum.
Use an inside micrometer and extension rods in order to measure the brake drum inside diameter.
Replace the brake drum if any of the following conditions exist:
| • | Any single brake drum inside diameter measurement exceeds the discard specification |
| • | Brake drum refinishing is required and any single brake drum inside diameter measurement exceeds the maximum refinish specification |
Out-Of-Round/Taper
Brake drum out-of-round or taper prevents accurate brake shoe adjustment, and is likely to cause excessive wear of other brake parts due to its eccentric action. An out-of-round drum can also cause severe and irregular tire tread wear, as well as causing brake pulsation.
Use an inside micrometer and extension rods in order to measure brake drum out-of-round and taper. Perform the measurements on the inboard edge and the outboard edge of the braking surface at 90 degree intervals. Refinish or replace the brake drum if the brake drum out-of-round or taper measurement exceed 0.15 mm (0.006 inch).
Runout
Excessive brake drum runout can cause brake pulsation. Measure the brake drum runout if the brake drum is suspected to be the cause of brake pulsation.
- Install the brake drum to the brake lathe. Follow the manufacturer's instructions.
- Use a dial indicator to inspect the drum braking surface. Refinish or replace the brake drum if the brake drum runout exceeds 0.15 mm (0.006 inch).
Balance
During manufacturing, weights are used to balance brake drums. Do NOT remove the balance weights from the brake drums. Perform the drum balance inspection on an off-vehicle wheel balancer. Replace the brake drum if the brake drum is out of balance.
