How do I adjust my bike brakes?

Rim brakes fall out of adjustment gradually as the pads wear and the cable settles, so the lever travel gets longer until one day it reaches the bar. The adjustment has an order, and doing it in the wrong order means redoing it.

Safety

What you'll need

• Allen keys, usually 4 and 5mm
• A 10mm spanner (optional)
• A rag

Step by step

1. Check the rim before anything else.Run a fingernail across the braking surface. Many rims have a wear indicator — a groove or a dimple — that disappears when the wall is worn out. A surface that is visibly concave, or where the indicator has gone, means the rim is finished. A worn-through rim wall can split under braking, which is why this check comes first and not last.
2. Check the pads.Look for the wear line moulded into the rubber, for grit and slivers of aluminium embedded in the face, and for hardening or glazing. Pads with metal in them cut rims quickly. Replace rather than adjust anything worn to the line.
3. Wind the barrel adjuster almost all the way in.The knurled barrel where the cable enters the brake or the lever. Winding it in first gives you the full range of fine adjustment later, once the coarse setting is made at the cable clamp.
4. Slacken the pad fixing bolt and set the height.The pad face should sit entirely on the flat braking track, roughly 1mm below the top edge of the rim, and not overhang the bottom. Squeeze the lever gently to hold the pad against the rim while you tighten it.
5. Set the pad angle square to the rim.Viewed from the side, the whole face of the pad should meet the rim, not just the top or bottom edge. Most pads have a domed washer stack that allows this to be set.
6. Add a small amount of toe-in.The front edge of the pad — the edge the rim reaches first — set about half a millimetre to a millimetre closer than the rear. Under braking the arm flexes and the pad lands flat. A pad with no toe-in is the usual cause of squeal.
7. Set the cable so the pads sit close.Slacken the cable clamp bolt, hold the arms so the pads are 1 to 2mm from the rim, pull the cable taut with pliers, and retighten. Do not clamp it with the pads touching — the brake will bind.
8. Fine-tune with the barrel adjuster.Wind it out to bring the pads closer as they wear. This is the adjustment you use week to week; you should rarely need the clamp bolt again until you fit new pads.
9. Centre the brake.Most calipers have a small centring screw on one arm; some are centred by tapping the whole caliper on its mounting bolt. Aim for equal gaps so one pad does not drag.
10. Check the lever travel.Squeeze hard. The lever must stop well before the handlebar with room for two fingers. If it reaches the bar, the cable is too slack or the pads are worn, and the bike is not safe to ride.
11. Test both brakes at walking pace before riding.Push off, roll, and apply each brake separately and hard. Listen for rubbing on a full wheel rotation and check the bike stops straight.

Tips

• Do one brake at a time so you always have a reference for how the other should look.
• Cables stretch most in their first few rides after fitting. Expect to take up slack once early, then rarely.
• A little grit embedded in a pad will score a rim in one wet ride. Pick pads over with a pin whenever you adjust them.

Common mistakes

• Adjusting the pads without checking the rim — A rim worn past its wear indicator can split at the braking surface under hard braking, usually at speed and usually with no warning. New pads on a finished rim make the problem worse, not better.
• Setting the pad so its top edge touches the tyre — It abrades the sidewall of the tyre every time you brake and will wear through it, which produces a blowout rather than a slow puncture. Always check the top edge of the pad has clearance.

If it doesn't work

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