Brake Noise

SCRAPING OR GRINDING, FRONT DISC BRAKES

Causes
- Front pads/linings worn down to the rivets or metal backing-plate.
- Excessive grooves in rotors.
- Rust or dirt accumulation on the rotor or caliper assembly.
- Damaged or bent pads/linings.

What to Check For
- Inspect linings and replace if;
- Excessively worn or grooved.
- Cracked.
- Bent or warped.
- Inspect the rotor for excessive grooves, resurface or replace as necessary.
- Verify the rotor splash guard is in place and that no debris is dodged in the caliper/rotor area.

SCRAPING OR GRINDING, REAR DRUM BRAKES

Causes
- Rear shoes/linings worn down to the rivets or the metal backing.
- Return springs broken or improperly installed.
- Drum friction surface cracked or excessively grooved.

What to Check For
- Inspect rear shoes/linings and replace if excessively worn or bent.

NOTE: To check if a brake shoe is bent or distorted, lay the shoe on its side on a flat surface. If the shoe wobbles it is not straight and should be replaced.

SQUEAL, FRONT DISC BRAKES

Causes
- Pads/linings are worn to minimum thickness, wear indicators are contacting rotors.
- Pads/linings are glazed.
- Pads are loose in the caliper housing.

What to Check For
- Inspect linings for;
- Minimum thickness, replace if necessary.
- Glazed appearance, replace if necessary.

NOTE: Brake linings become glazed as a result of overheating or brake drag. If the linings are glazed, first determine the cause before replacing them.

- Loose fit in the caliper. Crimp outer pad ears onto caliper housing, or replace missing or damaged anti-vibration clips. (As applicable.)

Anti-squeal Coating:

NOTE: Anti-squeal coating or pad insulator shims are very effective in preventing brake squeal on new brakes.

SQUEAL, REAR DRUM BRAKES

Causes
- Poor shoe to drum contact.
- Drums out of round.
- Shoes/Linings glazed (shiny, possibly black charcoal appearance).
- Weak or broken brake hold-down springs.
- Loose backing-plate, wheel-cylinder, or anchor.
- Excessive brake dust or debris in drum. Clean shoes and drums.

What to Check For
- Inspect drums for size and shape.
- Turn drums if bellmouthed or tapered.
- Replace drums if larger than maximum diameter.
- Inspect shoes/linings and adjustment.
- Readjust shoes if improperly adjusted.
- Replace shoes if glazed or excessively worn.
- Inspect brake hardware.
- Verify all return springs are installed properly.
- Replace all broken or distorted springs.

CLICKING OR RATTLE, FRONT DISC BRAKES

Causes
- Pads/linings loose in the caliper housing.
- Loose wheel bearings or grease cap.
- Loose lug nuts.
- Loose caliper mounting bolts.
- Caliper sticking or binding on the slides.

What to Check For
- Verify that the pads fit snugly in the caliper. If pads are loose, crimp outer pad ears onto caliper housing, or replace missing or damaged anti-vibration clips. (As applicable.)
- Adjust the wheel bearings and check that the axle nut cotter pin is not contacting the dust cap
- Loosen lug nuts and re-torque to the correct specification.
- Inspect and torque mounting bolts. Replace any missing or damaged hardware.
- Clean and lubricate the caliper slides.

Disc Brake Mechanical Force Diagram:

NOTE: Floating calipers require free and unrestricted movement on the caliper mounting. Floating or sliding calipers have pistons only on one side of the rotor. The first part of the piston's travel forces the inner pad against the rotor, then further travel forces the movable part of the caliper to pull the outer pad against the rotor.

CLICKING OR RATTLE, REAR DRUM BRAKES

Causes
- Rear shoes/linings binding against backing-plate.
- Rear shoes/linings sticking in grooves worn into Backing-platess.
- Loose backing-plate, wheel-cylinder, or anchor.
- Weak or broken brake shoe hold down springs.
- Cracked drum.
- Drum out of round.
- Shoes/Linings are bent or twisted

What to Check For
- Verify that the brakes shoes slide easily across the backing-plate. Lubricate backing-plate contact pads, remove any burrs or minor nicks.
- Inspect the shoe-backing-plate contact pads for grooves. Replace the backing-plate if any grooves are found.

NOTE: If you attempt to remove the grooves by grinding or filing, the new shoes/linings will not line up correctly with the drum. This may result in grabby brakes or a more pronounced clicking.

- Check and tighten the hold down bolts for the wheel-cylinder and backing-plate.
- Inspect all rear brake hardware (springs, clips, and pins) and replace if any defects are found.
- Measure the drum inside diameter at several points around the circumference of the drum. If the measurements vary by more than 0.002 inches, resurface or replace the drum.
- Inspect the drum for cracks or grooves, replace if necessary.

NOTE: Cracks in drums are often difficult to locate. To quickly determine if a drum is cracked lightly drop the drum (from a height of 4-5 inches) onto a flat hard surface. A cracked drum will make a dull thud sound while a good drum will make a ringing sound.

- Lay the shoes/linings on their sides on a flat surface, if the shoes do not lie flat replace them.