Brake Pull

FRONT DISC BRAKES

Causes
- Brake caliper piston seized, or frozen. A seized caliper piston will prevent the brake from being applied at that wheel. The vehicle will pull because one front brake is stopping the wheel, but the other isn't. The pull will be in the direction of the wheel that is stopping.
- Brake caliper sliding hardware seized, or frozen. Caliper slide assemblies which are seized, will prevent the outer pad from being applied, and reduce the braking action at that wheel.

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.

- Brake rotors or pads contaminated with oil or brake fluid. Oil and other contaminates fill and block the microscopic pores in the rotor's surface. This prevents the proper bonding of the brake lining to the rotor upon braking and greatly reduces braking performance.
- Worn front suspension components, or steering out of alignment. Braking will amplify these problems.
- Uneven tire pressure or tire size. Tire pressure and width directly affect the braking ability of each wheel. Uneven pressures and widths will result in uneven braking.
- Brake hose restricted or pinched.


What to Check For
- Verify that all four tires are the same size and that they are properly inflated.
- Inspect all brake lines leading from the master-cylinder to the calipers for evidence of pinching or deterioration.

NOTE: Inexperienced mechanics may sometimes clamp the flexible brake hoses with locking pliers while removing calipers. Closely examine the brake hoses for indentations or teeth marks. If any are present the hoses should be replaced. Brake hoses are double walled, damage to the interior pressure wall is not always visible.

- Inspect for free movement of caliper sliding or floating mechanism. Clean and lubricate as necessary.
- Inspect both calipers for uneven pad wear or signs of overheating (discoloration or glazed pad linings). Rebuild or replace both calipers if any defects are found.
- Inspect the linings and rotors for brake fluid or grease contamination. Any brake lining which has been contaminated should be replaced. The brake rotors should be thoroughly cleaned with a commercial brake cleaner.
- Check and adjust the front end alignment as necessary.

REAR DRUM BRAKES

Causes
- Right and left side brakes not evenly adjusted.
- Brake linings contaminated with brake fluid, gear oil or wheel bearing grease.
- Uneven tire pressures or tire size. Tire pressure and width directly affect the braking ability of each wheel. Uneven pressures and widths will result in uneven braking.
- Wheel cylinder seized. A faulty wheel-cylinder can cause uneven braking by failure to apply or to release pressure.
- Brake hose restricted or pinched.

What to Check For

- Verify that all four tires are the same size and that they are properly inflated.
- Inspect all brake lines leading from the master-cylinder to the calipers for evidence of pinching or deterioration.
- Back off the brake shoe adjustment on each side and readjust. After the brake adjustment has been made, firmly depress the brake pedal several times to seat and center the shoes, then recheck the adjustment.
- Inspect the wheel cylinders for signs of leakage or binding, replace or rebuild as necessary.
- Inspect the axle seals for signs of leakage. Gear oil leaking from the axle seal will usually be indicated by a spray pattern starting at the center of the drum and spreading outwards. If any signs of gear oil leakage are found, the shoes and seal should be replaced.

NOTE: Leakage at the axle seals is often caused by worn wheel bearings. If the vehicle has high mileage it is recommended to replace the wheel bearing along with the axle seal.