We often get asked how to adjust bike gears so this guide aims to cover the basics in setting up your gears and ensuring they stay running correctly. A lot of cyclists can find adjusting the gears a daunting prospect, but it isn't as hard as it seems and can actually be done quickly and easily at home or even out on the road or trail.
What Can Be Adjusted?
To try and simplify the whole thing we'll go through what can actually be adjusted in order to show that there isn't really much to the setup.
What Tools Will I Need?
The good news is that there aren't really any mega specialist tools involved in adjusting the gears on your bike. If you are just making adjustments to ensure that your gears are set up properly, or even just to learn a new skill, there shouldn't be any other components required either. Tools required to adjust gears are:
Making The Adjustments
As adjustments will involve you pedalling gently with your hands while altering the setup, it is recommended that you place your bike in a bike stand so that the rear wheel is off the floor and the bike is held securely. Common sense should be applied throughout - if it looks like your rear derailleur is going to go into the wheel at any point make sure you don't push it any further and the rear wheel isn't turning! To adjust the derailleurs it is best to disconnect the cable from the derailleur you are adjusting first, so it doesn't affect the movement of the derailleur itself.
To alter the B adjustment, press the derailleur towards the largest cog (you may need to gently pedal to let the chain move up along the cassette to allow the derailleur to move properly). The aim here is to have the top jockey wheel around 2mm away from the largest cog on the cassette. If the top jockey wheel is going to hit the cassette or is closer than 2mm, wind the B adjustment screw in (clockwise). If the jockey wheel is further than 2mm away from the largest cog on the cassette, wind the B adjustment screw out (anti-clockwise).
Adjusting Derailleur Limits
The rear derailleur has two limit adjustment screws; one for the low end of the cassette (the largest cog) and one for the high end of the cassette (the smallest cog). You may need to gently pedal the bike while making the following adjustments so that the chain allows the derailleur to move properly.
Locate the low adjustment screw (usually marked with an "L") and wind it in (clockwise) all of the way. Gently push the derailleur towards the largest cog until it won't go any further, caused by the limit screw. Continue gently pushing the derailleur towards the largest cog and slowly wind the low adjustment screw out until the top jockey wheel is in alignment with the largest cog on the cassette.
The high adjustment screw is adjusted in much the same way. Let go of the derailleur and gently pedal and the chain will work its way along the cassette towards the smallest cog. Adjust the high adjustment screw while continuing to gently pedal until the top jockey wheel is in line with the smallest cog on the cassette.
It is worth double checking the B Adjustment again at this point, just to be sure it is correctly set.
The last adjustment that can be made is through the Barrel Adjuster. Screw the barrel adjuster all of the way in, and then back it off a turn. With the shifter in the highest gear, connect the gear cable back up to the derailleur, ensuring that the cable is pulled tight. Start gently pedalling the bike and clicking through the gears. If you find that changing down the gears is initially unresponsive, it is likely the cable isn't tight enough so wind the barrel adjuster out a little. Repeat this until each gear goes in crisply and the chain runs without making a "clicking" noise or jumping.
Setting The Height
With the gear cable disconnected from the derailleur, push the derailleur out from the frame towards the largest chainring. The gap between the top of the largest chainring's teeth and the derailleur cage should be around 2mm. Reposition the derailleur on the mount or by moving the band if necessary to ensure this is the case, making sure that the derailleur remains parallel to the chainring.
Adjusting Derailleur Limits
Change the rear gears so they are in the largest cog of the cassette and make sure the chain is on the smallest chainring at the front. Adjust the inner limit screw so that the chain sits in the middle of the derailleur cage.
Change the rear gears so that the chain sits in the smallest cog of the cassette and push the front derailleur towards the largest chainring at the front, and make sure the chain is on that chainring. Adjust the outer limit screw so that while pushing the derailleur, the furthest it can travel leaves the chain running through the centre of the derailleur cage.
Screw the barrel adjuster all the way in, then out by one turn. With the shifters in the lowest gear at the front and in the middle of the gears at the back, pedal the bike until the front derailleur shifts the chain onto the smallest chainring and sits against the lower limit screw that you adjusted. Re-connect the cable to the derailleur, making sure it is pulled taut and wind out the barrel adjuster until changing up a gear on the shifter causes the derailleur to move straight away. If there is a delay in the derailleur moving due to slack being taken out of the cable, continue to wind the barrel adjuster out a bit at a time, until you can shift up and down chainrings without issue.
Gears won't go in properly, or some seem to work but others don't.
It is possible that your derailleur hanger is damaged so the derailleur isn't being held in the correct position. The solution would be to check the hanger and buy a new one if it is damaged. Don't be tempted to bend it back into shape as they are usually made from a softish Alloy material that will likely break either when you try and bend it, or even worse, when you are out on the road or trail pedalling under load.
Upshifting takes a lot of effort/force on the shifter.
This is likely caused by cable-drag. This is where the cable gets dirty or worn and friction between the inner and outer gear cables causes upshifting to require more effort than it should and changing won't be as crisp as it should be. Changing the inner cable will likely solve this issue.
Chain is slipping or jumping.
If your gears are set up correctly with the limit screws and b adjustment screws adjusted correctly, the likely cause of this is worn components. Sometimes slipping on the cassette can occur if the chain is replaced but the cassette has worn out. Slipping on the chainrings or chainsuck (where the chain is being pulled around the chainring at the bottom) usually indicates the chainring needs to be replaced. Another indication of a worn chainring with mountain bikes running a single ring at the front (1x) is that the chain will start to come off more frequently.
Hopefully this guide will have shown you how to adjust bike gears and given you the confidence so that you know how to adjust Shimano gears on a mountain bike or Sram gears on a road bike, but if you still have questions about this topic, or anything else, please get in touch. Our mechanics are all Cytech qualified and happy to discuss issues over the phone, or if you are near enough to us you can bring your bike to our dedicated Tech Centre to have someone take a look at it for you.