Cycle Maintenance - Adjusting indexed gears
an easy task
The dark art of indexed gear adjustment, made simple Nutty style.
Put the bike on a stand, or hang it from its saddle on a piece of strong string or rope so that you can turn the pedals and drive the rear wheel. Do not turn the bike upside down.
Check the chain is clean and lubricated. Check for chain wear. Check all the shifters are operational and not jammed.
Set the shifters to put the chain on the middle chain-ring (the smallest if you only have 2) and the smallest cassette cog (i.e. almost your hardest gear).
If the chain does not shift to the chain-ring then you will need to adjust the cable. Firstly find the adjuster (a barrel at one of the ends of the outer casing), then work out which way you need to turn it. If you need more tension in the cable to move the shifter then you need to unscrew the adjuster from its housing by a small amount. If you need less tension in the cable then screw the adjuster into its housing.
The secret is to think of the adjuster as an expanding section of cable outer. By unscrewing it from the housing you are lengthening the cable outer, and so putting the cable inner under more tension; and vice-versa.
If you run out of adjustment without fixing your gears then you will need to adjust the cable via its clamp. Return the adjuster to halfway between fully screwed in and fully removed.
Now locate the screw that holds the cable onto the shifter and slacken it off.
With one hand hold the shifter where it should be, with another hand pull the cable tight, and with your third hand do the screw back up tight. You can now use the adjuster to fine tune the gear shifter.
Now it’s time for the rear cassette. This looks harder, but is easy.
The three things to start are to ensure the shifter is set for the highest gear, the chain is on the smallest cog, there is no great amount of slack in the cable. If the cable needs a great amount of adjusting then adjust it at the screw in the same way as at the front.
However, before you even start to adjust anything you also need to locate the “stop screw” (here or here) which prevents the chain from travelling further and trying to shift to a non-existent cog. Make sure this is screwed in tight now. If it is preventing the correct gear selection then unscrew it until the chain can go onto the smallest cog.
Now turn the pedals. If the chain is trying to change down a gear, you have too much tension in the cable. Remove the tension as above, by screwing in the adjuster.
Once the chain is running smoothly change gear to the next gear down. If the chain does not change cogs you need more tension. Adjust as above by unscrewing the adjuster until the chain is happy changing between these two cogs when you move the gear lever.
Now change into the next gear down. It is likely that the chain will not move, but will be trying. Increase the tension by a quarter turn at a time (I find it helps to keep shifting between these three gears after each adjustment as you can knock the derailleur when adjusting it and get false results).
Once these three gears are adjusted, all the other gears should work. Test them. If they need fine tuning then you should be adept enough by now to increase or decrease tension in the cable to resolve the fault.
Once they are working fine, confirm this on the other chain-rings. The final test is to take the bike for a short test ride as sometimes the gears can behave slightly differently under pedalling pressure than under test pressure in a work stand.
Go to top of page.