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Spotting danger signs

The symptoms of some of the things that can go wrong with your bike are listed in this troubleshooting chart. It explains why a bike may be showing these symptoms and then suggests a solution, referring you to the pages where you will find a detailed sequence of steps to guide you.

If you still find the problem difficult to solve, consult the other section-specific pages of this web site for the specific part you are working on, so that you can understand it better. However, sometimes the symptoms confronting you can be due to a malfunction other than the one suggested in this chart. If you still cannot solve the problem, ask the technician at a good bike shop for help.


The chain will not shift onto a smaller cog or chainring.
Either grit has become lodged inside the cable housing or the cable lubrication has dried up.

Strip down the cables, flush the housings with degreaser, clean the loners with degreaser, lubricate, and reassemble.

The chain will not shift onto a larger cog or it shifts but does not run smoothly on it.
The cable has stretched or the relevant derailleur
poorly adjusted.

If the bottom bracket is a cartridge type, replace it. If it is an open-bearing bottom bracket, it may be possible to replace the worn bearings or bent axle.

The chain shifts cleanly, but jumps on the cogs when pressure is applied to the pedals.
Either the chain has a stiff link; or the chain or
cogs, or both, are worn; or a chainring may
be bent

Unclamp the cable at the derailleur, pull through any slack, and retighten. Then set up the derailleur.


The chain rubs on the inner then the outer side of the front derailleur cage. On a bike with a single chainring, the chain persistently falls off.
The bottom bracket is worn or its axle may be bent.

Cheek the chain for a stiff link and remove it if found. If no stiff link is found, replace the chain, If the problem persists, replace the cogs. If the chainring is bent, replace it.

When you apply the front brake and push the bike forward, the headset moves forward relative to the head tube.
The headset is loose or worn.
Strip and inspect the headset. Replace bearings if worn, regrease, and reassemble. Inspect the cups and races; if they are worn you should let a good bike shop replace the whole headset.
You hear a sudden snapping noise come from a wheel while riding and/or the wheel goes out of true.
A spoke may have broken. Replace the spoke and true the wheel.
There is side-to-side play of a hub on its axle, or when turning the axle in the hub you feel either a roughness or tight and loose spots.
The hub bearings are worn or, in the case of tight
and loose spots, the axle is bent.
Replace the bearings or the axle.
When pedalling forward, the cassette spins, but there is rio drive to the bike. Alternatively, the cassette spins before the drive is engaged or there is much side-to-side play in the cassette.
The freehub body is worn. Replace the freehub body.
The brakes are hard to apply, and/or sluggish to release.
Grit and dirt is inside the cable housing or the lubrication on the inner cables has dried up.
Strip down the cables, flush the housings, and clean the inner cables with degreaser, lubricate both, and reassemble.
You have to pull the brake lever a long way before the brakes engage.
The pads are wearing down or the cable has slipped through the clamp bolt.
If the pads are not too worn, take up the extra travel by unelamping the brakes, pulling the cable through the clamp, and tightening. If the pads are worn, replace them.
The two brake pads do not contact the braking surface at the same time.
Your brakes are not centered.
Follow the procedures for centering the type of brakes on your bike.
The brake pads contact the braking surface without pulling the lever too far, but are ineffective at slowing the bike.
There is grease on the pads, foreign objects are embedded in them, or they are wearing unevenly. You may even need a different compound of brake pad.
Rub the pads with emery cloth. Remove foreign bodies with needle-nose pliers. Fit new pads if they are worn unevenly. Seek advice from a bike shop regarding different pad compounds.
The fork regularly reaches the limit of its travel (bottoms out).
With air/oil forks, not enough air is in the system. With coil/oil forks, too light a spring is fitted.
Pump in more air. Replace springs with heavier-duty springs.
On steep, smooth descents, the rear wheel lifts under braking.
The front of the bike is diving under braking because the fork is not stiff enough.
Pump in air, or increase preload, according to the type of fork on your bike.
The front wheel judders up and down when cornering.
The fork’s rebound is set too fast.
Use the relevant adjuster to reduce the speed of the forks rebound.
A rear air/oil shock regularly reaches the limit of its travel (bottoms out).
Insufficient air in the shock, or too much damping, means that the shock is not returning from each compression quickly enough.
Set up the sag on the shock again. If the problem continues, use the damping adjustment to speed up the action of the shock.


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Spotting danger signs