Cleaning disc brakes safely

The rule

Nothing oily touches a rotor or a pad. Not degreaser, not chain lubricant, not penetrating spray, not a cloth that has wiped a chain.

Why pads cannot simply be cleaned

Brake pad friction material is porous. Oil that reaches it soaks in, and what has soaked in does not come out with a solvent — it comes back out under heat, which is exactly when you need the brake.

Most manufacturers state that contaminated pads are replaced. That is their instruction and it governs.

Cleaning a rotor

Use a cleaner the manufacturer specifies for the purpose, or isopropyl alcohol where the maker permits it, on a clean cloth that has touched nothing else. Wipe both faces.

A rotor that has been contaminated and cleaned will often still squeal until the pads are bedded again — the manufacturer publishes a bedding procedure involving a series of controlled stops.

Preventing it during a wash

Take the wheels out before using any degreaser. It takes thirty seconds and it removes the risk entirely.

If the wheels stay in, turn the bike so the drivetrain faces away from the discs, and remember that aerosol overspray travels considerably further than the nozzle suggests.

Handling pads and rotors

By the edges. Skin oil on a braking surface is enough to cause squeal, and it is the reason mechanics handle new rotors through a cloth.

When to stop and go to a shop

Any spongy lever, any reduction in power that cleaning does not fix, a rotor that is scored or heat-discoloured, or a leak of any kind. Braking is a safety system and this site reports manufacturer procedure rather than improvising around it.