Check your brakes
Ten minutes a month to make sure the bike stops when you want it to. You check the levers, how worn the pads are, and that the disc or rim is clean.
What you need
- A torch
- A hex key (often 4 or 5 mm)
- Isopropyl alcohol and a clean rag (to clean a disc)
When to do it
- Once a month, and before a long ride or a descent.
- As soon as the braking changes: softer lever, noise, the bike stopping less well.
- After a crash or after transporting the bike (a lever or caliper may have moved).
Which brakes do you have?
| Brake | How to spot it | What wears out |
|---|---|---|
| Disc | a metal disc bolted to the hub, squeezed by a caliper | the pads, and eventually the disc |
| Rim (V-brake, caliper) | rubber pads that squeeze the edge of the rim | the pads, and the rim itself |
A disc brake can be mechanical (cable-operated) or hydraulic (operated by fluid, with a hose instead of a cable).
Steps
1. Test the levers
Squeeze each lever hard, standing still. It should go firm and stop well before the bar: at least a finger's width. On a hydraulic brake, a lever that sinks further each time you pump it, or stays soft, means there's air in the system: it needs bleeding, best left to a bike shop if you've never done it. The fluid depends on the brand and is never interchangeable: mineral oil for Shimano, DOT fluid for SRAM. The right one is written on the lever or caliper; mixing them destroys the seals.
On a cable brake, look at the cable at the lever and the caliper: it mustn't be frayed or rusty.
2. Check the wear
Disc brake: shine the torch into the caliper from above or behind. Each pad is a metal backing plate (1) with friction material (2). Shimano says to replace them when 0.5 mm of material is left (3); SRAM, when pad and backing plate together are under 3 mm. Order new ones at about 1 mm: beyond the limit, the backing plate rubs on the disc and destroys it. Check the disc too: a minimum thickness is engraved on it (often "MIN TH 1.5 mm"); below that, it must be replaced. The Replace your pads guide explains how.
Rim brake: look at the pads. They have grooves (4); once the grooves are gone (5), replace the pads. Check the rim too: braking wears it, slowly. Many have a wear indicator on the braking surface: either a groove all the way round, which fades as it wears, or a small hole that appears once the rim is too thin. If the groove has gone, the hole shows, or the braking surface looks dished, the rim could fail: take it to a shop.
3. Check the contact
Rim brake: squeeze the lever and watch the pads. They must meet the rim flat, across their whole surface, lined up with the top of the braking surface but never on the tyre (they would cut it), and without hanging below the rim. Ideally the front of the pad touches a fraction before the back: that's "toe-in", which stops the brake squealing.
Disc brake: spin the wheel. A slight intermittent rub is common; constant rubbing, or a wheel that slows quickly, means the caliper is off-centre. Loosen its two mounting bolts, squeeze the lever so it centres itself, and tighten the bolts again while keeping the lever squeezed.
4. Check it's clean
The disc or the rim's braking surface must be clean and dry: no oil, no shiny residue. Clean a disc with isopropyl alcohol on a clean rag, never with chain degreaser or anything that leaves a film.
5. Test while riding
At low speed, somewhere clear, brake with each brake on its own. The bike should slow down clearly and smoothly, without judder or vibration. The front brake is the most powerful: apply it progressively, without grabbing it.
Check it's done right
- Both levers are firm and stop well away from the bar.
- There's more than 1 mm of material on the pads, or grooves on the rim pads.
- The rim pads touch the rim, not the tyre.
- The bike stops cleanly, with no unusual noise.
Common mistakes
- Waiting for the metallic grinding: that's the backing plate rubbing, the disc is already damaged.
- Touching the disc or pads with greasy fingers, or splashing them when lubing the chain.
- Forgetting the rim: on a bike with rim brakes, it's the rim that wears out in the long run.
What next
Log the check in your logbook. If the pads need replacing, follow the Replace your pads guide. Bleeding a hydraulic brake and replacing a worn disc are jobs for a bike shop, or for when you have some experience.
Sources
This guide was checked against the following documents:
- Shimano, brake technical documents (pad wear, rotors)
- Park Tool, Linear Pull Brake Service (pad adjustment)
- road.cc, How to tell when your wheel rims have worn out
- road.cc, How to clean disc brakes (SRAM on contaminated pads)
- Competitive Cyclist, Shimano mineral oil vs SRAM DOT fluid
Values vary between models: your part's manual always takes precedence.