Adjusting the Rear Gears

I must state that the information supplied here is for use at your own risk. If you are not sure on how to do this, then do not do it. If you have friction shifters, this adjustment is not necessary except to tighten any slackness in the gear cable.

In this article we will only look at adjusting the cable tension to make the gears change smoother. We will not be touching the stop screws which stop the chain coming off of either end of the gear cluster. Below is a picture of a typical rear cluster and derailleur system.

The photograph is a view showing the rear gear cluster and plastic guard to stop the chain from getting jammed in the spokes. In case you were wondering what some of the other things are, here is the explanation:

• A - Plastic guard to stop chain from jamming in the spokes if it falls off of the top cog;
• B - Thumbscrew adjuster for changing the tension on the gear cable. Used to adjust the indexing;
• C - Rear Derailleur limit stop adjusting screws; and
• D - Mounting point for a BOB YAK rear trailer.

In the photograph the only part that we are interested in is B, the thumbscrew adjuster (also called a cable adjusting barrel), which is used for changing the tension on the gear cable. This is what is used to keep the indexing of the shifter aligned with the actual gear cogs on the cluster.

Most derailleurs operate by starting at the smallest cog with no tension and are pulled up the gear cluster by the gear lever. Each click in the gear shifter should pull the derailleur in towards the wheel and thus pulling the chain up to the next larger cog.

It is when the tension gets out of adjustment as the cables stretch that the gear lever's indexing no longer works correctly. Another thing to note with this type of derailleur system, is that if your were to snap the gear cable, the derailleur will immediately jump to the smallest cog as there is no longer any tension on the cable. There are some models of derailleur that work in the opposite direction.

For the sake of this article, we will presume that your cables, gear shifters and rear derailleur have already been set up and have been in use. You will need to raise the bike up off of the ground. I usually suspend the bike form the washing line with some cargo straps.

You then need to shift the gears so that the chain is on the second smallest cog. Once this is done, you also need to make sure that the gear shifter lever is in the corresponding position. On an eight speed system, the lever should read 7 when the chain is on the second smallest sprocket.

The reason that we don't use the smallest sprocket is because adjusting it one way will run it up against the stop which stops the chain coming off of the gear cluster. By using the second smallest cog, as we play with the tension, we can hear the chain start to make a noise as it shifts to the smallest cog.

Performing this adjustment is easier if you have someone to help by turning the pedals for you. Firstly you will need to locate the cable adjustment barrel on your derailleur. Then get your assistant to slowly turn the pedals. As they are turning the pedals, you will need to turn the adjusting barrel so that it applies tension to the gear cable. This is normally done by turning it anti clockwise.

If you hear the chain start to make a noise, and look like it is about to drop to the smallest cog, then you are turning the adjustment barrel the wrong way.

As the pedals are turning slowly, turn the adjustment barrel (normally anti clockwise) until you hear the chain start to make a noise as if it is about to change up onto the third smallest sprocket. Once you hear this noise, stop winding. Turn the barrel in the opposite direction very slowly until the noise stops.

Whilst turning the pedals, change the gears up and down the entire range of the rear gear cluster. If it is still not changing properly, then you may need to tweak the tension with the cable adjustment barrel slightly.

If shifts to larger gear cogs are slow, then you need to turn the adjustment barrel anti clockwise a little. If changes to smaller gears are slow or hesitate, you will need to release tension slightly by turning the adjustment barrel clockwise.

Once you have all the gears shifting properly there is one more thing that you need to do, which some people neglect. You need to take the bike for a ride and shift through all of the gears whilst riding. If the gears are still jumping, noisy or not changing properly, then you will need to take it to a bike mechanic. This also applies if you were unable to get the adjustment correct whilst the bike was hanging on the washing line.

If you are unable to get the correct adjustment, or there are still problems whilst riding, you could have a stretched chain, worn gear clusters, or a bent or damaged rear derailleur. This is best checked by taking your bike to a bike shop or mechanic as they have specialised tools for checking the wear and tear on a chain and gear system.

I also use this method when I replace the gear cable or fit new parts in the gear system. It usually has to be done several times as the cables stretch. Since I have gone back to using friction shifters which do not use indexing, this type of adjustment is not required.