Brake Maintenance: Pads, Rotors and Bleeding
Brakes are the one system you cannot ride around. A few minutes checking pads and rotors keeps them sharp, and bleeding is a job you can learn safely.
Brakes earn their keep every ride, and like most parts they wear slowly rather than failing suddenly. Checking pads and rotors regularly is easier than fixing a brake on the trail.
Check the pads
Look into the caliper with a light and check how much pad material is left above the backing plate. Most pads have a wear line or a minimum thickness marked by the maker. If the friction material is thinner than about 1 mm, or the wear spring shows, replace both pads as a pair.
- Common sign of wear: levers travel further before the brakes bite.
- Uneven wear: a sticky piston, or a caliper that needs realigning.
- Contaminated pads: replace them; do not try to degrease friction material.
Bedding in new pads
New pads and rotors need bedding in before they give full power. Find a dry, safe stretch of road or trail and do several firm stops from a moderate speed, letting the brakes cool between runs. You are transferring an even layer of pad material onto the rotor, which is what makes braking smooth and strong.
Never spray oil or degreaser near a rotor or pad. Contamination is the most common cause of a brake that squeals or pulls.
Cleaning a glazed or squealing brake
A brake that squeals can often be fixed by removing the pads, cleaning the rotor with isopropyl alcohol on a clean rag, and lightly rubbing the pad surface on fine abrasive paper on a flat surface. Refit, realign the caliper so it is parallel to the rotor, and bed the pads back in.
Rotors and alignment
A rotor that rubs when the wheel turns is usually slightly bent or the caliper is off-centre. Loosen the caliper bolts, squeeze the lever to centre the caliper, and tighten again. A bent rotor can often be straightened carefully by hand; if it has deep grooves or is below the minimum thickness stamped on it, replace it.
Bleeding: when and why
Hydraulic brakes feel spongy when air or moisture is in the line. A bleed replaces the fluid and removes air; the procedure differs by brand, so follow the maker's guide and use their fluid and fittings. If a bleed feels beyond you, a shop can do it quickly, and it is safer than guessing on a brake that stops you.
Check pads monthly, bed them in properly, keep oil away, and your brakes will feel the same in October as in April.
Frequently asked questions
When should I replace brake pads?
When the friction material is about 1 mm or less, or when the lever travel grows noticeably. Replace both pads in a pair and bed them in before riding hard.
Why do my disc brakes squeal?
Usually contaminated or glazed pads. Clean the rotor with isopropyl alcohol, lightly sand the pads, realign the caliper and bed them in again.
Do I need to bleed my brakes?
Bleed when the levers feel spongy, which means air or moisture in the line. Procedures differ by brand, so follow the maker's guide or have a shop do it.
