Replace a gear or brake cable
A rusty or frayed cable makes shifting vague and brakes spongy. Replacing it, with its housing if needed, brings back crisp shifting and a firm brake lever.
What you need
- A new cable of the right type (gear or brake) and cable end caps
- Housing of the right type, with its ferrules, if it needs replacing
- Cable cutters (ordinary pliers crush the housing and fray the cable)
- A fine point (awl or needle)
- The hex keys for your derailleur or brake
- A little chain lube
When to do it
- The cable is frayed, rusty, or kinked near the lever or the clamp bolt.
- Shifting is poor although the derailleur is well adjusted, or the lever returns slowly.
- The brake lever feels spongy, sticks or doesn't return properly.
- The housing is split, crushed or kinked.
Cable and housing
The cable (3) is the steel wire that pulls. The housing (1) is the tube guiding it between the lever and the derailleur or brake. Its ends take a ferrule (2), and the cable is clamped under a clamp bolt (4) then cut, with a crimped end cap (5) so it doesn't fray.
Gear housing and brake housing are not the same:
| Gears | Brakes | |
|---|---|---|
| Housing | "compressionless" housing: steel wires running lengthways, most often 4 mm in diameter | wound housing: a single steel wire coiled round |
| Don't | never use it on a brake: it can burst under braking force | don't use it for gears |
Braided housing (a Kevlar braid around the liner) works for both. For brakes, the cable head depends on the lever: a pear or mushroom shape for a drop-bar lever, round for a flat-bar lever.
Steps
1. Get ready
- Gear cable: shift to the smallest sprocket at the back (and the smallest chainring, for the front cable). The cable is then at its slackest.
- Brake cable: open the brake's quick release if it has one, or unhook the guide tube of a V-brake.
Note or photograph the cable's path: which stop, which hole, which side of the clamp bolt.
2. Remove the old cable
Loosen the clamp bolt (4). If the cable end is kinked or frayed, cut it just before the damaged part: it will slide through the housing more easily. Then pull the cable out through the lever:
- Trigger shifter: depending on the brand, a cover or a screw gives access to the cable head. Push the cable to pop the head out.
- Drop-bar lever: the cable exit is often under the hood, the lever's rubber cover. Push the cable as close to the lever as possible: the head comes out through that hole.
- Flat-bar brake lever: line up the slots of the barrel adjuster and its locknut with the lever's slot, then free the cable and its head.
3. Replace the housing if needed
If the housing is in good shape, keep it. Otherwise, cut the new one to the same length as the old one, with cable cutters, nice and square. Cutting often squashes the liner: open it up with a fine point so the cable slides freely. Fit a ferrule (2) on each end if it fits into the part the housing goes into; if it doesn't, that part is made for bare housing.
Housing should be as short as possible, but enter each stop in a straight line, and let the handlebar turn without pulling.
4. Thread the new cable
Lightly lube the cable with a little chain lube, on the first few centimetres that will go into the housing. Hook its head into the lever, then feed it through each length of housing and each stop, to the derailleur or brake, following your photo.
5. Tension and clamp
Lay the cable in the groove under the clamp bolt, pull the slack out by hand, then tighten the bolt. Park Tool gives about 5 Nm for a derailleur bolt; for a brake, follow its manual.
6. Bed the cable in
A new cable and its housing settle with use. Gears: hold the derailleur and work the shifter several times. Brakes: squeeze the lever hard about ten times. If slack appears, loosen the bolt, re-tension and retighten.
7. Cut and crimp
Cut the cable about 30 mm past the clamp bolt (6) and crimp an end cap (5) onto it, with crimping pliers (many cable cutters have a crimping section).
8. Adjust
- Gears: set the limit screws and indexing: see Adjust your rear derailleur.
- Brakes: set the clearance and centring: see Adjust rim brakes. Close the quick release.
Check it's done right
- Every gear shifts, without noise or hesitation.
- The brake lever is firm, springs back on its own, and stays well clear of the bar when squeezed hard.
- The handlebar turns from side to side without the housing pulling or the gears changing.
- The cable end has its end cap.
Common mistakes
- Gear housing on a brake: it can burst under braking.
- Cutting housing with ordinary pliers: it gets crushed and the cable drags.
- Not bedding in the new cable: slack appears after the first ride.
- Housing too short: it pulls when you turn the bar.
What next
Log the change in your logbook. After a ride or two, the new cable will have slackened a little more: a few turns of the barrel adjuster take up the play.
Sources
This guide was checked against the following documents:
- Park Tool, Shift Cable Replacement: Trigger Shifters (removal, 5 Nm, 30 mm, end cap)
- Park Tool, Shift Cable Replacement: Drop Bars (drop-bar levers)
- Park Tool, How to Size and Install Shift Cable Housing (housing types, 4 and 5 mm, cutting, ferrules, bedding in)
- Park Tool, Brake Housing & Cable Installation: Upright Bars (brake housing, cable heads)
Values vary between models: your part's manual always takes precedence.