Drum Brake System: Adjustments

Fig. 5 Rear Drum Type Brakes:

Self-adjusting shoe mechanisms assure correct lining-to-drum clearances at all times. Fig. 5, The automatic adjusters operate only when the brakes are applied as the vehicle is moving rearward.
Although the brakes are self-adjusting, an initial adjustment is necessary after the brake shoes have been relined or replaced, or when the length of the star wheel adjuster has been changed during some other service operation.
Frequent usage of an automatic transmission forward range to halt vehicle motion may prevent the automatic adjusters from functioning, thereby inducing low pedal heights. Should low pedal heights be encountered, it is recommended that numerous forward and reverse stops be performed with a firm pedal effort until satisfactory pedal height is obtained.
If a low pedal height condition cannot be corrected by making numerous reverse stops (provided the hydraulic system is free of air), it indicates that the self-adjusting mechanism is not functioning. It will be necessary to remove brake drums, clean, free up and lubricate the adjusting mechanism. Then adjust the brakes, being sure the parking brake is fully released.

Fig. 6 Backing Off Brake Adjustment By Disengaging Adjusting Lever:

INITIAL ADJUSTMENT

1. Remove adjusting hole cover from brake backing plate and from the backing plate side, turn the adjusting screw upward with a screwdriver or other suitable tool to expand the shoes until a slight drag is felt when the drums are rotated.
2. Remove the drum.
3. While holding the adjuster lever out of engagement with the adjusting screw, fig. 6, back off the adjusting screw about one full turn with the fingers. If finger movement will not turn the screw, free it up. If this is not done, the adjusting lever will not turn the screw during vehicle operation. Lubricate the screw during with oil and coat with wheel bearing grease. Any other adjustment procedure may cause damage to the adjusting screw with consequent self-adjuster problems.
4. Install brake drum and wheel, and adjusting hole cover. Adjust brakes on remaining wheels in the same manner.
5. If pedal height is not satisfactory, drive the vehicle and make sufficient reverse stops with a firm pedal effort until proper pedal height is obtained.

BRAKE SHOE ADJUSTMENT GAUGE

Fig. 5 Brake adjustment with gauge:

1. Use the brake shoe adjustment gauge shown in Fig 4 to obtain the drum inside diameter as shown. Tighten the adjusting knob on the gauge to hold this setting.
2. Place the opposite side of the gauge over the brake shoes and adjust the shoes by turning the adjuster screw until the gauge just slides over the linings. Rotate the gauge around the lining surface to assure proper lining diameter adjustment and clearance.
3. Install brake drum and wheel, final adjustment is accomplished by making several firm reverse stops, using the brake pedal.