Repair guides › Brakes
Replace rim brake pads
The older rim brake on 1980s–2000s mountain, touring and cyclocross bikes: two short arms on frame bosses, joined by a straddle wire above the tire. It squeezes pads on the rim like a V-brake. The brake cable stops at a hanger above the tire and pulls a yoke up the middle of a straddle (link) wire, which pulls both arms in. Pads are usually smooth-post, held by an eye bolt so you can set height, angle and toe. They need road-style (short-pull) levers, not V-brake levers.
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Tools
- Ball-end hex key set (1.5–10 mm): Park Tool HXS-1.2 Professional L-Shaped Hex Set ($$)
- 1/4" click torque wrench (about 2–17 Nm) + bits: Pro Bike Tool 1/4 inch drive click torque wrench set (2.2–16.9 Nm) ($$)
- Shop rags + nitrile gloves: shop towels and nitrile gloves ($)
- Isopropyl alcohol 91%+: isopropyl alcohol 91% ($)
- Metric combination wrenches 8–17 mm: TEKTON 14-pc metric combination wrench set 6-19 mm ($$)
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Steps
- Check the wear line or grooves on each pad. Replace when the grooves are almost gone (about 1 mm left), or if the pad is hard, cracked or has metal bits stuck in it.
- Match the pad type (see the pad diagram): threaded post with a nut (V-brakes, U-brakes), smooth post with an eye bolt (cantilevers), road cartridge (holder plus slide-in insert) or short threaded road pad (side-pull calipers). Left and right pads are often marked; the closed end of a cartridge faces forward.
- Remove the old pad, keeping the curved washers in the same order: they let you angle the pad.
- Fit the new pad loosely. Squeeze the brake so it sits flat on the rim's braking surface, about 1 mm below the top edge, never touching the tire.
- Toe-in: the front of the pad touches the rim first, about 1 mm ahead of the back (a folded business card behind the pad's tail helps). This stops squeal.
- Tighten the pad nut or eye bolt (about 5–8 Nm) while holding the pad still. Re-check that it did not twist.
- Wipe the rims with isopropyl alcohol and reset cable tension so the lever stops well before the bar. Test both brakes before riding.
Torque
| Fastener | Torque |
|---|---|
| Pad nut / eye bolt | 5–8 Nm |
Diagram
Close-up of the partsRim brake pads
Signs it needs doing
- Squeal or shudder (pads not toed in, or a loose cable hanger)
- Lever pulls to the bar
- One pad drags (spring tension)
- Weak braking