Disc Brake System: Testing and Inspection
BRAKE PAD INSPECTIONRemove the pads/linings from the caliper and inspect for the following:
- If the linings (pads) are worn to within 0.030 inch (0.762mm) of the shoe, or rivets, replace both sets of shoe and lining assemblies, (inboard and outboard) on the front wheels.
NOTE: It is necessary that both front wheel sets be replaced whenever a respective shoe and lining is worn beyond specifications or damaged.
- Lining damage. The lining should not be cracked or glazed (shiny, glass or charcoal like appearance).
- Check the flatness of the pads/linings. Place the inboard and outboard lining surfaces together and check for a gap between the lining surfaces. This gap should not exceed 0.13 mm (.005-inch) at the middle of the lining surfaces. This applies to new or used pads/linings.
Replace the pads/linings if any problems are found.
The disc pads/linings have a wear indicator that makes a noise (metallic squeal) when the linings wear to a degree where replacement is required.
BRAKE CALIPER INSPECTION
Inspect the caliper for the following problems:
- Brake fluid leakage near or around the piston dust boot.
- Cracked caliper housing or piston.
- Uneven brake pad wear.
- The inner pad is worn more than the outer pad.
- The pads/linings from the left caliper are worn more than the right caliper (or vice versa).
- Missing or damaged mounting hardware.
- Caliper slide joints, slide pins, and bushings are free of corrosion and nicks
- Tears or cracks in dust boots around caliper pistons and slide assemblies.
- Evidence of excessive heat:
- Bluish purple discoloration of rotor or caliper housing.
- A thin brick red oxidation layer evenly covering all brake components on the hub assembly (not to be confused with the typical rough, and flaky oxidation caused by rust).
- Linings should maintain light contact with the disc or have no more than 0.005 inch clearance.
- If the truck was braked to a stop shortly before checking clearance, it is normal for the brakes to drag.
- If the linings are more than 0.005 inch from the disc, apply the brakes several times and recheck the clearance.
If any problems are identified with the above areas, the calipers should be replaced or rebuilt.
The Following Areas Should Also Be Inspected:
- Inspect the flexible brake hoses for cracks or signs of leakage. Replace if any defects are found.
- Inspect the splash guard around the rotor for damage or loose mounting bolts.
NOTE: The splash guard should not he permanently removed. The splash guard helps prevent debris and water from contacting the pad and caliper assembly and also helps funnel air across the brake components to assist in cooling.
- Inspect rear brake operation and adjustment. Rear brakes which are out of adjustment will require the front brakes to do more work, causing accelerated wear and possible overheating.
Check adaptor plate to knuckle bolts for specified torque:
- 110 foot pounds (149 Nm)