how_to_hyd-brk

SINGLE-SERVO Vs. DUO-SERVO

1. SINGLE-SERVO: Single plunger coming from the wheel cylinder, most commonly used with Surge Brake applications.

2. DUO-SERVO: Two plungers coming from the wheel cylinder, stops vehicle in both forward and reverse directions.

SELECTING HYDRAULIC BRAKE PARTS:

1. Determine the size of brake.
a. Measure the diameter of the mounted brake shoe.
b. Measure the width of the lining.

2. Determine the manufacturer of the brake.
a. Is the manufacturer's name on the backing plate?
b. Compare to complete Brake Assembly or to exploded drawings onsite.

3. Select each part needed. If looking for complete assemblies and see a "PARTS ONLY", there is NOT an assembly and
drawings should be used to select individual parts for repairs.

REASONS WHY BRAKE HARDWARE SHOULD BE REPLACED

1. Worn, weak return springs will cause the brake linings to drag against the drum and cause premature brake failure.

2. Hold down springs will lose their tension and allow the brake shoes to wobble or ride up aainst the face of the brake
drum, causing premature lining failure.

3. A frozen adjusting screw will not allow shoes to be adjusted properly.

4. Rubber dust plugs will crack with age and allow dirt to contaminate linings.

5. A stretched self-adjusting cable or worn lever prevents the self-adjusting lever from properly aligning the shoes.