When to replace bike brake pads

The rule

Replace disc brake pads when the friction material is down to 0.5 mm. That is Shimano's limit: its dealer manuals say not to use pads with 0.5 mm or less of pad material. SRAM uses a different measurement: replace the pad when backing plate plus friction material measures less than 3 mm. Rim brake pads are done when the wear grooves are gone.

In distance, a typical set of resin disc pads lasts about 2,000 km (1,250 miles), metal pads about 3,500 km (2,200 miles) and rim pads about 3,000 km (1,850 miles), in dry, hilly riding. Pad life varies hugely. One wet, gritty descent can finish a set: check after every muddy ride. These kilometre figures are LeCoach rules of thumb, not manufacturer data. This calculator is one of the free LeCoach cycling calculators.

Flat riding stretches these figures; mountain riding shortens them a lot.

The signs: how to check

• Disc: measure the pad. Remove the wheel and look into the caliper with a torch, or take the pads out. Less than 0.5 mm of friction material (Shimano) or under 3 mm pad plus plate (SRAM) means replace. This is a hard sign.
• Rim: wear grooves gone. Rim pads have grooves or a wear line moulded in. When the surface is flat to the line, replace them. Also a hard sign.
• Metal-on-metal grinding. A harsh scraping noise usually means the backing plate is touching the rotor or rim. Stop riding the bike and replace the pads straight away: this is a hard sign, and it damages rotors and rims quickly.
• Lever travels further than before. On hydraulic disc brakes the pistons self-adjust, but thin pads can still change the lever feel. On rim and cable brakes, longer lever travel is a common wear sign.
• Squealing that cleaning does not fix. Contaminated or glazed pads often squeal and lose power. Oil-contaminated pads cannot be saved.
• Braking power down. If you need to pull much harder to stop, check the pads.

Check your pads every 1,000 km or once a month, and after every wet or muddy ride.

Estimate yours

• Kilometres on these pads. Count from when you fitted them.
• Pad type. Sets the starting point: about 2,000 km for resin disc pads, 3,500 km for metal disc pads and 3,000 km for rim pads.
• Conditions. Mixed weather cuts the estimate by 30 %, often wet riding by 60 %. Water and grit grind pads down fast.
• Terrain. Flat riding adds 30 %. Mountains cut the estimate by 40 %, because long descents mean long, hot braking.
• Rider and bike weight. At 90 kg or more combined, the estimate drops by 15 %.

Under 80 % used is "Fine for now", 80 to 100 % is "Check it soon" and 100 % or more, or any hard sign, is "Replace it".

Resin, metal or rim pads

Resin (organic) disc pads are quiet and bite well, but they wear faster, especially in the wet, and fade sooner on long descents. Metal (sintered) disc pads last longer and handle heat better, but can be noisier. Some rotors are marked for resin pads only, so check yours before switching. Rim pads wear the pad and the rim, and wear fastest when grit sits on a wet rim.

Common mistakes

• Waiting for the noise. By the time the backing plate grinds, the rotor or rim is already being damaged.
• Measuring the wrong thing. Shimano's 0.5 mm is friction material only; SRAM's 3 mm includes the backing plate.
• Touching pads or rotors with oily hands, or spraying chain lube near them. Contamination ruins pads.
• Skipping the bed-in. New pads need a series of firm stops to reach full power. Follow the maker's instructions.
• Forgetting the rotors. Rotors wear too; check the minimum thickness marked on the rotor or in the manual.

When the estimate changes

• Wet winters, gravel and mud can wear out a set in a ride or two. Muddy MTB rides are the extreme case; see the mountain bike tire pressure calculator for setup on the same trails.
• Mountain holidays with long descents use pads far faster than flat riding.
• Heavier riders and loaded bikes need more braking force for every stop.
• Braking style matters. Short, firm braking wears pads less than dragging them all the way down a hill.

Keep pads in step with the rest of the bike using the bike maintenance schedule, when to replace bike tires and when to replace a bike chain. Ask LeCoach anything about your riding and your next event, and it answers from your own rides.