How to: Gears

Adjusting cable tension for correct shifting

Gear systems often need fine tuning and maintenance to keep them running smoothly. With indexed gear systems, an over stretched gear cable is often the culprit for your gears failing to engage correctly. Below we will explain hot to fix this common problem.

adjusting gears labelled

(1) Shift into a gear where the cable feeding the derailleur is at its slackest making sure the shifter is pushed all the way to the end of its travel.

(2) Now locate the adjusting barrel on the derailleur (there may also be an adjuster on the shifter, but this should be used for ‘on the fly’ adjustments). Turning the adjusting barrel anti-clockwise (towards the wheel) has the effect of taking up excess slack in the derailleur cable.

(3) Click up one gear at the shifter (be careful to make sure it’s just one), move away from the shifters and start to turn the pedals.

(4) While you are turning the pedals, turn the barrel adjuster anti-clockwise until the chain jumps into the desired gear.

(5) Keep on pedalling and turn the adjuster further clockwise until the chain is about to go into the next gear. At this point turn the barrel adjuster back towards you by a full turn.

(6) That should be it, now simply go up and down the gears making sure they are working well. If you are having trouble dropping down to the smaller sprockets you may have the cable tension too high, so turn the barrel adjuster clockwise by one complete turn again and retest.

(7) For non indexed systems or situations where you are in danger of completely unscrewing the barrel adjuster, just loosen the cable inner wire anchor bolt and pull the slack out of the wire. Then retighten the bolt.

Other problems:

(1) If you can’t engage a high gear (smallest sprocket) no matter what you do, the cable is probably the culprit. Replace the sticky or rusted cable, and the problem will usually go away.

(2) If you have done everything right, but the bike still doesn’t shift reliably, the most common reason is that the chain and sprockets are too worn to work properly. If you replace one, you must replace both. A new chain on old sprockets or visa versa usually skips, and the new part wears out very quickly. To avoid this, it is worth investing in a chain checker with which you can periodically look for chain wear.

(3) A final possibility is a bent derailleur. Derailleurs become bent when the bike falls over on the right-hand side. Whenever you set a bicycle down, or put it in a car, set it on its left side to protect the derailleur.

Glossary of Terms

Friction shifters

With friction shifters, changing gears requires you to push or pull the gear lever to move the chain to a different sprocket, you then need to make fine adjustments to the lever to center the chain on the desired sprocket or chainring.

Indexed shifters

Index shifting is a system where the control has discrete stops. Hub gears, gripshifts and rapid fire shifters are all indexed systems. Each stop (click) on the shifter corresponds to one position of the derailleur. This allows the cyclist to change gear without having to adjust each time, as in friction shifting.

Gripshifts. Often found on hybrid bikes and mountain bikes.

Downshifters. Often found on older road bikes. These shifters are mounted on the downtube of the frame and can be indexed

Rapid fire (trigger) shifters.  Used on Hybrid/Mountain Bikes.

STI shifters: Found on newer road bikes, the Shimano Total Integration (STI) shifters combines the braking and gear shifting controls into the same component. This allows shifting gears without having to remove a hand from the bars, unlike with previous downshifters.

Front Mech (derailleur):  The front mech is used to move the chain between the front chainrings.

Rear Mech (derailleur):  The rear mech is used to move the chain between the rear sprockets.

Hub gears.  A hub gear is an enclosed system of gears in the rear wheel (hub) of the bike. The advantage is that they are fairly maintenance free.

Freewheel: A complete unit consisting of a group of sprockets and a freewheel assembly. The freewheel assembly allows the pedals to remain stationary while the bicycle is in motion, so that the rider can coast.

Freehub an cassette: Works in the same way as the freewheel above, but the freewheel component is actually a part of the hub called the freehub. The cassette is a separate cluster of sprockets that slides onto the freehub body.

Chain:  The chain and gears wear out very easily if not maintained correctly.  One of the most important things to do is to make sure your drivetrain is clean and well lubricated.