Servicing the front brakes usually corrects pulsation in the brake pedal. Service the rear brakes only if the problem persists.

When removing the brake drums perform the following actions:

Normal light scoring of the brake drum surfaces will not affect brake operation. Normal light scoring must not exceed 0.51 mm (0.020 inch) in depth.

Notice: Be careful not to drop the brake drum during handling. An out-of-round condition can occur from even the smallest fall, which may result in brake pulsation.

A cracked drum is unsafe. Replace any cracked drum. Do not attempt to weld a cracked drum.

Smooth any slight scores. Heavy or extensive scoring causes excessive brake lining wear. Refinish the drum braking surface if necessary.

Perform the following steps if the brake linings are slightly worn (but still reusable) and the drum is grooved:

1. Polish the drum with a fine emery cloth.
2. Do not refinish the drum.

Eliminating all of the grooves in the drum and smoothing the ridges on the lining would require the removal of too much metal and lining.

The grooves and the ridges will match if the grooves and the ridges are left alone. Satisfactory service can be obtained.

Refinish an excessively grooved drum if replacing the brake linings. A grooved drum will wear a new lining. The excessive wear will cause difficulty when obtaining proper brake performance.

An out-of-round or tapered drum prohibits accurate brake shoe adjustment. An out-of-round or tapered drum may cause excessive wear on other components of the brake mechanism. An out-of-round or tapered drum may also cause the following conditions:

Refinish the drum in order to true up the braking surfaces when the drum exceeds the specification limits in taper and/or out-of-round. Use the J 22364-01 or an inside micrometer fitted with proper extension rods in order to measure out-of-round and taper wear.

Measure for out-of-round and taper wear at the following locations:

If a drum must be refinished, remove only enough metal to obtain a true, smooth braking surface. If a drum does not clean up when refinished to a maximum rebore diameter, replace the drum. Removal of more metal will affect heat dissipation. Heat dissipation may cause drum distortion.

All brake drums have a maximum diameter cast into them. The diameter is the maximum wear diameter and not a refinish diameter. Do not refinish a brake drum which does not meet the specifications at the end of this section. Replace the brake drum if necessary. Refer to Component Specifications .

When refinishing a brake drum, resurface the drum to a dimension no more than 0.76 mm (0.030 in) less than the discard diameter.

The refinish diameter is the maximum diameter the drum may be refinished to and still allow safe braking action. If the dimension is exceeded, the brake drum will wear beyond the discard diameter during normal brake wear.

Always use sharp cutting tools or bits. Dull or worn tools leave a poor surface finish which will affect initial braking performance. Always use vibration dampening attachments when refinishing braking surfaces. The attachments eliminate tool chatter so that a better finish can be obtained.

The optimum speed for refinishing braking surfaces is a spindle speed of 200 rpm. Cross feed for rough cutting should range from 0.25 to 0.15 mm (0.010 to 0.006 in) per revolution.

Ensure that the finish cuts that were made at cross feed do not exceed 0.05 mm (0.002 in) per revolution.

After cutting on a brake lathe, finish the surface with 80 to 120 grit emery cloth backed with a flat piece of steel or wood, while the lathe is running. Finishing will break up any threading left from the cutting tool.

Manufacturers use weights in order to balance brake drums during manufacturing. Do not remove the weights.

Inspect the brake drums for damage if one of the following conditions exists: