How to Adjust Your Gears

By Tim Brennan

If your gears are the type that snaps from one gear to the next, then sooner or later they will need adjusting. They will need this fine tuning when they start jumping between sprockets even though the gear shifter is in the correct position. It’s perfectly normal for new bikes to need gear adjustments after a short period, just because the cables stretch a little with use.

Calibrating your gears is just simply a process of shortening or lengthening the gear cable so that the two gear changing arms (called a mechs or derailleurs) correctly line up with the chain wheels (or sprockets). Funny word derailleur, guess it must be a French word that describes "de-railing" the sprockets... Anyway, you can also adjust how far the derailleurs are allowed to move so that they don't push the chain off the end of the sprockets.

Sometimes derailleurs get seized up, especially if they are not regularly lubricated or cleaned. Before you start making adjustments, make sure all the joins of the derailleur are oiled - this just might solve the problem with no extra work.

Before you start, check that none of the sprocket teeth and both mechs are not excessively worn or bent.

The best position to put the bike in upright, but off the ground. A bike stand is the ideal way to support your bike while you adjust your gears. The reason for this is that when the rear mech is upside down it sometimes behaves differently than when it is the right way up. It can be really frustrating if you get your gears precisely adjusted and running like a dream, only for them to be still jumping when you go to ride it. This is not always the case - you can often get away with turning the bike upside down. If this doesn't work you will have to adopt the more lengthy process of cycling a bit, looking and listening for jumping gears, getting off to adjust and repeating until they don't jump.

To adjust the gears, each derailleur has three screws that you can tighten and loosen as necessary. Next to the derailleur, look for where the plastic cable tube ends and start to see the metal cable again. You will notice that there is a screw that the cable goes through with a locking nut on it. This lengthens and shortens the cable. There are two screws that limit how far the mechs can move. They are labeled H and L - this stands for High and Low. On the rear the H screw stops the chain falling off the small sprocket and the L screw is for the large sprocket end. The opposite is true for the front mech.

The technique that I use is to put it in the gear that continually jumps - I then look at the lever to see which position it is in. I then use the lengthen/shorten screw to get the chain on the right sprocket according to the lever - listening to make sure it is smooth. This process needs to be repeated over and over in lots of different gear combinations. Some manufacturers recommend against using the top gear on one mech and the lowest gear on the other, since the chain doesn't like to bend sideways. You might want to ignore these combinations if you have a mountain bike with loads of gears.

When you have got the lengthen/shorten screw in exactly the right place use the lock nut to make sure it stays put.

The H and L screws don't have to be altered that often, just when the chain has trouble getting onto the last sprocket or if it keeps falling off the end. To adjust them you'll need a screw driver - you can figure out which way to turn by looking at the mech or just turning and seeing which way it moves the mech. These screws will only move the mech when it has been positioned at the far ends of its movement.

This process works for me most the time - good luck.