Why pads deserve a regular look
Brake pads are designed to wear. Each time you brake, a little of the pad material is rubbed away, and eventually there is not enough left to do the job. Worn pads can reduce stopping power, damage the rim or disc, and in the worst case leave metal rubbing on metal. Checking them takes a minute and costs nothing.
Brakes are a safety system, so treat this article as general information. The exact markings and replacement steps depend on your brake type, so follow the manufacturer’s instructions and see a bike shop if you are unsure.
Know which brakes you have
Most bikes use one of two broad types.
- Rim brakes squeeze rubber or similar pads against the wheel’s rim. The pads are usually visible from the side as small blocks in holders, often called shoes.
- Disc brakes squeeze pads against a metal disc, called a rotor, attached to the wheel hub. The pads sit inside a caliper next to the rotor, so they are harder to see.
Some bikes have other systems, such as drum or hub brakes, which are not covered here.
Checking rim brake pads
Look closely at each pad while the wheel is stationary.
- Wear indicators. Many rim pads have grooves, lines or a marked limit moulded into the rubber. When the grooves are gone or the pad reaches the line, it is worn. If your pads have no marking, check the maker’s information.
- Overall thickness. A pad that looks very thin or has little material left above the holder is near the end of its life.
- Uneven wear. One end of the pad worn more than the other, or one side of the bike worn more than the other, suggests the brakes need adjusting.
- Hardening and cracking. Old pads can harden, glaze or crack even if they look thick. A shiny, glassy surface can reduce grip.
- Embedded debris. Small stones or metal particles pressed into the surface can scratch the rim. Removing them is a job for careful, correct tools, or for a shop.
- Alignment. The pad should meet the rim’s braking surface squarely. A pad that touches the tyre can wear the tyre, and one that sits too low can slip off the rim.
Also look at the rim itself. A groove, scoring or a rim braking surface that looks worn thin is a reason to ask a mechanic for advice, because rim wear can become a safety problem.
Checking disc brake pads
Disc pads are harder to inspect because they are hidden in the caliper. You can usually look from the side or from underneath, with the wheel on.
- Look through the caliper. You should be able to see the pad material between the metal backing plates and the rotor. If you can barely see any pad material, or the gap looks very small, the pads are likely worn.
- Compare both pads. If one looks much thinner than the other, the caliper may not be moving evenly, which a shop can look at.
- Check for contamination. Pads that look oily or glazed, or a rotor with oil on it, can brake poorly and squeal. Lubricant, certain cleaners and fingerprints can all cause problems, so keep chain lube and sprays away from brake surfaces.
- Remove the wheel if the maker allows it. Taking the wheel out gives a clearer view, but do not squeeze the brake lever while it is out, because it can make the pistons move closer together and complicate refitting.
Some brakes have specific wear limits stated by the maker, and that information is more reliable than guessing.
Signs you can feel and hear
Even without looking, your bike may give clues:
- Squealing or grinding. A high squeal can be caused by dirt, contamination or vibration. A harsh metal grinding noise can mean the pad material is gone and the backing plate is touching the disc or rim. Stop riding and have it checked.
- Longer stopping or a weaker feel. If you need to squeeze harder or earlier than before, something has changed.
- Lever travel. On rim brakes, worn pads can mean the lever pulls closer to the bar before the brakes bite. On hydraulic disc brakes, the lever may get closer to the bar as pads wear, although a spongy feel can also mean air in the system, which needs a shop.
- Pulsing or uneven braking. This can suggest a warped rotor or a rim with a flat spot.
A quick brake test in a safe, empty area, rolling slowly and squeezing each lever in turn, is a good routine. It also helps you practise good braking control.
When to replace the pads
As a general rule, replace pads when:
- Any wear indicator shows they have reached their limit.
- Very little pad material remains.
- They are cracked, glazed, contaminated or unevenly worn.
- You hear metal-on-metal grinding.
- The brakes feel noticeably weaker and cleaning and adjustment do not fix it.
Replacing pads early is cheap compared with replacing a damaged rim or rotor. Pads wear faster with heavy loads, steep descents, wet and gritty conditions, and frequent hard stops, so riders in those conditions need to check more often. Regular wet weather riding, for example, tends to be hard on pads.
Doing it yourself or using a shop
Replacing pads is within reach for many home mechanics, but the procedure varies a lot between rim brakes, mechanical discs and hydraulic discs. Pads must be the correct type for the brake, installed the right way round, and aligned properly. After any pad change, test the brakes carefully before you ride, and bed new pads in as the maker describes.
Take the bike to a shop if you are not comfortable with the job, if the brakes feel spongy, if there is oil contamination, or if the rim or rotor looks damaged. A mechanic can also check cables, hoses and levers while the pads are being looked at.
A sensible habit
Look at your pads whenever you clean the bike, and again before long trips or descents. Keeping an eye on them is one of the simplest ways to protect your braking, but it does not replace a periodic professional check. If you ever doubt that your brakes will stop you, do not ride until they have been looked at.