A worn brake cable -- or damaged cable housing -- makes it harder to apply the brakes, and can keep the
brakes from rebounding fully away from the rim. Damaged derailleur cables make
shifting to a smaller cog or smaller chainring unreliable.
If the cable is only dirty, it can be cleaned out, and may work good as new.
See our section on cable cleanout.
Check the cable housing (the sections of big black tube that surround the
cable). If you see a sharp bend, the housing needs to be replaced. Look at
the exposed sections of cable. If you see fraying, breaks in the individual
wires, or loosened wires, the cable itself must be replaced.
To replace a cable, buy a new cable, a section of cable housing, a cable
end-cap, and housing end-caps. First thing you should know: brake cable
housing has metal wrapping that goes in a circle around the cable, while
derailleur cable housing has metal strips that run the length of the cable.
Derailleur cable housing has a smaller hole (for the smaller cable) than brake
cable housing. Don't substitute one type of cable housing for the other!
||Undo the cable at the far end (at the brake mechanism
or at the derailleur) by loosening the bolt on the retaining clip. Remove the
cable end-cap by compressing it on the sides opposite the crimp with
needle-nose pliers, or simply cut the cable.
Slide the cable housing caps away from the housing. Now slide caps and
housing off the cable.
As you remove the old cable,
place the parts in a line, so you can easily see where everything goes. Even if
you're planning to replace the housing, keep the old sections so you can cut the
new pieces to match!
Remove the old cable from the handlebar end.
||Brake Cable: With the cable loose, pull the lever all
the way back to the handlebar. This should expose a retaining clip, or a
hole in the handle itself, that contains the barrel on the end of the
Pull the barrel out of the retainer by lining it up with the slot in
||If you have slots in your cable-tension adjuster and in the
housing of the lever, you can simply slide the cable out the side of the
housing by lining the slots up. Otherwise, pull the entire length of the
cable out of the brake.
Brake cable being pulled out of the
|Index Shifter with cable-access cap: An access port
makes cable replacement easy (example, Shimano XTR shifters). Locate the
cable cap. Unscrew it to expose the shifting mechanism.
|Shift into the smallest cog or chainring (where the cable
will be the most loose). You'll see the end of a cable-barrel rotate into
Shove back on the cable so the barrel comes out of the shifter
mechanism. Grab the barrel and pull the cable through.
||Index Shifter without access port: Click the shifter
down into the smallest cog or chainring. Unscrew the bolts on the underside of the shifter. You may need a jewelers screwdriver.
(In most cases, removing the bolts on the gear indicator gauge won't
expose the cable housing. But if you can't see any other way to
disassemble the shifting unit, try it.)
||Once the you're into the guts of the unit, push back gently on the cable until the barrel
comes out of the retainer. Now grab the barrel and pull the cable out.
While you're at it, clean the exposed surfaces, and clean the cable
pathway into the barrel adjuster.
|Grip Shifter: Pull the hand grip away from the
shifting grip. (Wet the inside of the grip to make it slide.) Or, loosen
the brake and shifter attachments so you can slide the shifter away from
|While pulling the shifting knob away from the body of the
shifter, rotate until you find the position where the shifting knob will
pull away from the housing.
|Push backwards on the cable to pop the barrel out of the
shifting grip. Take a long look at the path of the cable, so you can put
the new cable back on the same course.
Grab the barrel and pull the cable out of the shifter.
|While you're at it, clean up the inside of the shifting
mechanism. Grip shifters tend to accumulate a lot of dirt and sand.
Cut the sections of new cable housing to match those you're replacing. A
Dremmel tool is good for getting a clean cut through the metal of the housing.
A cable-cutting tool will also make a nice slice through the housing. A
fine-toothed hacksaw will do.
||Insert the new cable through the mechanism at the handlebar,
making certain it's seated properly in its retainer. Then begin assembling the sections of cable housing onto the cable.
Slide on the front end cap, cable housing, and back end caps for each section
of housing. Fit the housing into the mountings at the handlebars, and at each
relay mounting of the frame.
||Dial the cable-tension adjuster down at the handlebar
(clockwise when viewed from the cable), then turn it back one turn. This
puts the cable in its starting position. If it's a rear derailleur cable,
also screw in the cable-tension adjuster at the derailleur.
Check to be sure the cable-housing caps are secure, and that the housing is
nestled in the relays at each section. Test the derailleur or brakes to make
sure the cable is working. Now cut the cable, leaving about 3 inches.
Use a special cable cutter, or a
Dremmel tool, to cut the cable! If you try to cut it with pliers, you may
delaminate the cable.
||Put on the
cable cap. If you don't have a crimping tool, you can use needle-nose pliers to grasp the shaft of the cap
and squish it down tightly onto the cable.
|This is what happens when you don't use a cable cap. This
derailleur cable has frayed badly, so it can't be adjusted at the
retaining clip. And it can't be disassembled and cleaned -- it can only be
Perform final adjustments of the cable tightness with the barrel adjuster.
For derailleur cables see the section on tuning the front
or rear derailleur. For brakes, see the brake
[Fix-it Index Page]