Brake Grab

FRONT DISC BRAKES

Causes
- Brake rotors and pads contaminated with oil or brake fluid.
- Caliper mounting bolts loose.
- Caliper piston sticking. The piston may be sticking or becoming wedged in the caliper bore due to accumulated corrosion deposits or excessive wear. A sudden drop in pedal height followed by wheel lockup indicates a sticking piston.

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.

What to Check For
- 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 the caliper mounting bolts and tighten as necessary.
- Check for free movement of caliper slides and pistons. Inspect piston and slide boots for cuts or tears. Look for signs of moisture contamination of slides or leakage from piston seals. Check for binding of piston when retracting into caliper bore with bleeder open. Rebuild or replace as necessary.