Bike brake fluid, mineral oil and cleaner

Mineral oil or DOT fluid: which fluid for your brake?

A hydraulic disc brake transfers the effort from the lever to the caliper via a liquid contained within the hose. There are two types that coexist and do not mix: mineral oil, notably used by Shimano, Tektro and TRP, and DOT fluid, which is of the same nature as that used in cars, chosen by other manufacturers. Each system, including seals, is designed for a single type: an unsuitable fluid can render the brake inoperative. The type to use is indicated in the manual and often on the lever or reservoir cap. DOT fluid absorbs moisture from the air, gradually lowering its boiling point: it needs to be replaced according to the manufacturer's schedule.

Bleeding a hydraulic brake: when and with which equipment?

A bleed refreshes the fluid and removes air bubbles from the system. It is necessary if the lever feels spongy, after a hose shortening, and at the frequency set out in the manual. Prepare the right fluid, a bleed kit suitable for the brake brand, with a syringe or funnel and fittings, a spacer to insert between the pistons, gloves, and cloths. Remove the wheel and pads before starting, so no drops reach them. Without tools or experience, entrust the task to a workshop.

Brake cleaner: discs and pads free from grease

A brake that squeaks, vibrates, or loses power often has a contaminated disc or pads: overspray from chain lube, greasy fingers, or bleed drops. A special brake cleaner, designed to leave no greasy residue, dissolves these deposits; apply it with the wheel removed and pads taken out, then wipe with a clean cloth. A pad soaked in oil cannot be recovered well: replace it.

Other maintenance products and good deals

Lubricants and greases can be found on the bike grease page, cleaners and degreasers for the rest of the bike in the maintenance products, to be kept away from the brakes. The bike maintenance section also covers tyre repair. End of range at clearance, new products in the new arrivals.

Which brands for brake maintenance?

Motorex, based in Langenthal, Switzerland, offers an aerosol brake cleaner.

Shimano provides the mineral oil intended for its hydraulic disc brakes, in a bottle for bleeding.

Finish Line offers a disc brake cleaning spray.

TRP, a brake brand associated with Taiwanese manufacturer Tektro, sells its mineral oil in a 100 ml bottle, compatible with hydraulic TRP and Tektro brakes.

Velox, a French spare parts brand, offers Brake Cleaner, an aerosol brake cleaner for disc brakes.

Frequently asked questions

Which brake fluid should be used in a bike?

The one specified by the brake manufacturer, indicated in the manual or on the lever: mineral oil or DOT fluid, sometimes with a brand-specific oil. They do not mix.

Can DOT fluid be used in Shimano brakes?

No. Shimano hydraulic brakes operate with the brand's mineral oil; using DOT fluid may damage the seals. If a mistake is made, have the brake checked by a workshop.

When should you bleed your bike's brakes?

When the lever becomes soft, returns closer to the handlebars, or brakes unevenly, after a hose change, and at the frequency recommended in the manual, which should be more frequent for DOT fluid.

How do you clean a bike brake disc?

With the wheel off and pads removed, spray a special brake cleaner on a clean cloth and wipe both sides of the disc. Do not use chain degreaser or polish, as they leave a film.

Why does a disc brake squeak?

Often due to contamination of the disc or pads, a poorly aligned caliper, or new pads that haven't yet bedded in. Clean, check the alignment, then bed in with several progressive brake applications.