Why bike brakes squeak
Brakes squeak when something makes the pad and the rim or rotor vibrate. The usual causes are:
- Contamination: oil, grease, chain lube, or road grime on the braking surface.
- Glazed pads: a shiny, hardened surface from heat or contamination.
- Misalignment: the pad or caliper sits at an awkward angle.
- Embedded debris: grit or metal particles stuck in the pad.
- New pads: many need a short break-in period.
- Wet weather: some noise in the wet is common and often fades as the surfaces dry.
Start with the simplest and least invasive fixes, and re-test after each one.
Rim brakes: clean, resurface, toe-in
- Clean the rims with isopropyl alcohol or soapy water and a clean rag, removing grime and dust. Keep fingers off the braking surface afterwards.
- Inspect the pads. Pick out any embedded grit with a small pick or screwdriver. If the surface is hard or shiny, lightly rub it flat with fine sandpaper on a flat surface. If the pads are worn or heavily contaminated, replace them.
- Toe in the pads. The front edge of the pad should touch the rim a very small distance before the rear edge, so the pad does not vibrate as it drags along. A common trick is to place a folded piece of card behind the rear of the pad while you tighten the pad bolt, then remove it. Keep the angle small.
- Check pad height, so the pad hits the rim and not the tyre.
Pads that touch the rim unevenly may also need centring. See fixing front brake rub, which covers rim brake adjustment.
Disc brakes: clean, realign, bed in
- Clean the rotor with isopropyl alcohol or a brake cleaner meant for bike disc brakes, applied to a clean, lint-free rag. Avoid spraying cleaner onto the pads.
- Check the pads. Remove them and look at the surface. If they look oily or shiny and glazed, they can sometimes be lightly sanded, but pads soaked in oil are often better replaced. Many manufacturers advise replacing contaminated pads, so follow your brake maker’s guidance.
- Realign the caliper. Loosen the caliper bolts a little, squeeze and hold the lever, and tighten the bolts gradually while holding it.
- Bed in the brakes. Many disc pads and rotors benefit from a bedding-in procedure after cleaning or fitting new parts, such as repeated firm (not full-stop) brake applications at moderate speed. Procedures vary, so check the manufacturer’s instructions for yours.
- Replace worn parts. Pads worn very thin, or a rotor that is worn or damaged, can cause noise and reduce braking.
If the brake is noisy and also weak, see disc brakes with no stopping power.
Can you use WD-40 or lubricant on squeaky brakes?
No. Lubricants and penetrating oils on rims, rotors, or pads can contaminate the friction surfaces and seriously reduce braking power. Do not spray WD-40, chain lube, or similar products on or near the brakes. If this has happened by accident, clean the rim or rotor with isopropyl alcohol, and replace the pads if they have absorbed the product.
Also take care when lubricating the chain, since overspray can reach the rotor; how often to lube a bike chain explains how to apply just enough.
Why do my brakes squeak when the pads are good?
Good pads can still squeak because of dirty rotors or rims, glazing, loose mounting bolts, poor alignment, or something specific to the pad compound. Some pad types, such as certain metallic or sintered disc pads, are commonly reported to be noisier in wet or cold conditions. A little noise in the rain is usually less concerning than noise that persists in dry weather.
Squeal when you are not braking
A sound that appears when you are not braking is usually a rub, not a braking squeal. Spin the wheel and look for contact. A caliper that is slightly off-centre or a rotor that is slightly bent can cause it. Fix it with the steps in fixing front brake rub. If the pads do not release, see brakes that will not spring back.
When to replace pads
If squealing continues after cleaning and alignment, if the pads are worn to the wear indicator, or you hear metal grinding, replace the pads. Grinding can mean the friction material is gone, and continued riding can damage the rim or rotor. If you are unsure, a shop can check quickly. For cable slack or lever feel after a pad swap, see how to adjust rear bike brakes.
FAQ
Can you put WD-40 on squeaky bike brakes?
No. It can contaminate pads and braking surfaces and reduce stopping power.
What can I put on my brakes to stop squeaking?
Nothing is usually needed on the braking surfaces. Cleaning with isopropyl alcohol, correct alignment, and replacing contaminated pads are safer fixes.
Why do my bicycle disc brakes make noise?
Common causes are contamination, glazed pads, misalignment, a bent rotor, or wet conditions.