Braking creates a little noise from the friction of the pads on the braking surface. That’s normal. What isn’t is squealing, squeaking, screeching, whining, rasping, grinding or any other noise that’s bad enough to set your teeth on edge. The pads aren’t clamping onto the rim or rotor like they’re meant to, and instead are slipping, intermittently gripping, rubbing, or causing vibration. Fixing this can mean a trip to the bike shop – brake squeal is occasionally very persistent – but with some basic tools like Allen keys you can often sort this yourself.
Are they clean? Whatever kind of rim brakes you’ve got – sidepull, V-brake, or cantilever – the pads need to strike the rim cleanly. If they can’t because the rim is dirty with mud and brake pad residue, it’s time to get cleaning. Sometimes a bit of grit becomes embedded in a pad, which will score the rim. Dig it out carefully with a sharp knife.
Check for wear. Brake pads wear away – eventually down to the metal backing plate, which will rasp and damage the rim. Fit new pads before this happens! If the pads are more than half worn, or have less than a few millimetres remaining, it’s time for new ones.
Check they’re set up properly. Check that the brake moves only how it’s supposed to. The calliper shouldn’t move fore and aft, the brake pads shouldn’t be loose in the calliper, and if the brake has cartridge pads (where you replace just the pad material not the metal fixings too) check they’re secure in their metal holders. Adjust the brakes until they’re working effectively. If they’re still squealing with the pads parallel to the rim, ‘toe in’ the pads. This means angling the pads so the front ends (in the bicycle’s direction of travel) are 1-2mm closer to the rim. Quality rim brakes have concave and/or convex washers to make this easy to do. Slide a bit of cardboard between the rear end of the brake pad and the rim to set the toe in, or temporarily wrap a cable tie around the rear of the pad.
Check the rim is true and undamaged. Spin the wheel. If it wobbles, true it. If it’s dented or cracked, get your bike shop to replace the rim.
Try new pads. Hard, plasticky-feeling pads are noisier and don’t work as well. Try brake pads with a softer compound, such as Kool Stop Salmon or Fibrax Red. They won’t last as long, but they will be grippier and quieter
Are they clean? Dirt, grease or grime on the rotors or the disc pads compromises braking and creates noise. After washing your bike as normal, spray the rotors and pads with disc brake cleaner (a solvent) and wipe down with a lint-free cloth or paper towel. You can do this without disassembly. See ‘refresh your pads and rotors’ for how to do a more thorough job.
Check for wear. Once the pad material is gone, you’ll be braking with the metal backing plate on the metal rotor, which is noisy and dangerous. Replace the pads before this! When the pad thickness is down to a millimetre or less, replace the pads. This will also prevent the thin disc pad spring, which keeps the pads apart, from coming into contact with the rotor.
Check they’re set up properly. Check that the calliper if fixed firmly to the frame or fork. Adjust the brakes until they’re working effectively. A common problem is the calliper not being centred over the rotor, so it rubs the pad on one side, giving a ‘shh, shh’ sound as the wheel turns. If your bike has cable disc brakes with a single moving piston, bear in mind that the fixed piston won’t retract when you release the lever – use the bolt or dial on the wheel side of the calliper.
Check the rotor is true and undamaged. Rotors can become bent quite easily. Spin the wheel and look at the rotor edge on. If it’s wobbly, gently bend it with an adjustable spanner to remove the worse of the kinks. If it can’t be straightened satisfactorily, or if the surface is damaged – for example, scored by worn disc pad – replace the rotor or get your bike shop to do it for you.
Refresh your pads and rotors. Still noisy? The pads might be contaminated or pitted or even glazed over, and there may be issues with the surface of the rotor. Before replacing either, there’s something else you can try. You’ll need disc brake cleaner, wet-and-dry sandpaper, lint-free cloths or paper towels, workshop gloves, and the tools to remove the rotors (probably a T25 Torx) the pads (possibly nothing). Remove the rotors and pads. Clean them with disc brake cleaner and wipe dry. Then firmly sand each rotor’s outer ring where the brakes bite on them. Don’t forget to do both sides. Then apply disc brake cleaner again to remove any grit and wipe dry. Then take each pad and rub it on clean sandpaper in a circular motion. Apply disc brake cleaner again and wipe dry. Refit the rotors, pads, and wheels.
Try new pads. Sintered pads (which have metal particles in the pad material) are the longest lasting but, especially in the wet, are noisier than either organic pads (which don’t) or semi-metallic pads (which are sort of a cross between organic and sintered pads). A different type of pad – or even, sometimes, a different brand – can eliminate brake squeal.
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