Nothing is more frustrating than poorly indexed or sticky gears. When you start to go uphill and need to shift down, you want the shift to happen instantly instead of the chain skipping around or making a horrible grinding noise as it doesn’t quite reach the next cog. By learning how to adjust mountain bike gears, you can ensure that your shifting is always perfect and you will not have to rely on your local bike shop making adjustments for you.
Here at The Adventure Junkies, we want you to be able to carry out minor maintenance tasks on your bike so we have written this guide to help you adjust your gears the next time they need some attention.
Fortunately, once you have gotten your head around what each of the screws on a derailleur does, adjusting your gears is not as hard as it might sound. If you are unfamiliar with the different components, have a look at the explanation below of each of the parts that make up your bike’s gears.
CHAINRING: The cog or cogs attached to the cranks.
CASSETTE: The nest of cogs on your back wheel.
DERAILLEUR: This is the moving part that pushes the chain from one cog or chainring to another.
LIMIT SCREWS: These screws decide how far the derailleur can move. There is an upper and a lower screw. They need to be properly set, otherwise, the derailleur will push the chain too far or not far enough. If a chain falls between the cassette and spokes, the chain or wheel can get damaged.
B LIMIT SCREW: This adjusts how far below the cassette the derailleur hangs.
SHIFTER: Attached to the handlebar, a shifter pulls or releases a cable attached to the derailleur, making it move the chain between cogs.
INNER CABLE: A metal wire connected to the shifter and derailleur
OUTER CABLE: The inner cable runs through an outer cable to help keep it tight.
Now you know what each of the parts are and what they do, you can follow the instructions to adjust your gears. You will need hex keys and possibly a screwdriver.
Putting your bike in a workstand will make your life much easier. Thoroughly clean your bike before getting started as this will make working on it much more pleasant. Furthermore, dirty components can be the cause of poor shifting.
Photo by istockphoto.com/portfolio/gielmichal
HOW TO ADJUST THE REAR DERAILLEUR – 7 STEPS
STEP 1: MOVE THE CHAIN TO SMALLEST COG
Use your shifter and turn the pedals to move the chain onto the smallest cog. If it won’t move that far, then leave it as far as it will go.
STEP 2: ADJUST THE BARREL ADJUSTER
On the shifter, where the cable goes into the body, you will find a barrel adjuster. This is a screw that can be tightened or loosened to adjust cable tension. Screw it all the way in and then unscrew it a couple of turns.
STEP 3: UNSCREW THE BOLD HOLDING THE CABLE IN PLACE ON THE DERAILLEUR
Unscrew the bolt holding the cable in place on the derailleur. Turn the pedals and use your hand to push the derailleur towards the spokes. It should not be possible to push the chain further than the biggest cog. If this is possible, then you need to adjust the limit screw.
If you are lucky, the screw will be marked with an L. If not, you may need to look up your derailleur online to find out. Adjust the screw so that the chain cannot be pushed too far.
STEP 4: MOVE CHAIN BACK ONTO THE SMALLEST COG
Gently allow the derailleur to move the chain back onto the smallest cog. Check the alignment and adjust the other limit screw as needed.
STEP 5: REMOVE ANY INNER CABLE SLACK
Make sure the cable is under the retaining bolt and tighten it to hold the cable in place. Cycle through the gears a couple of times before shifting down to the biggest cog. Release the retaining screw, pull the cable tight and do up the screw again. This will remove any inner cable slack.
STEP 6: SHIFT THROUGH THE GEARS
Shift through the gears one by one. The shifting should be smooth going onto each cog. If shifting onto bigger cogs is slow, unscrew the barrel adjuster half a turn and try again. If shifting onto smaller cogs is slow, tighten the barrel adjuster half a turn.
STEP 7: ADJUST THE FRONT DERAILLEUR
If you have a 1X transmission (one chainring at the front and 10, 11 or 12 cogs at the back), then you are now done. If you have more than one chainring, you will now need to adjust the front derailleur.
HOW TO ADJUST THE FRONT DERAILLEUR – 7 STEPS
STEP 1: MOVE CHAIN ONTO BIGGEST COG
Use the shifters and turn the pedals to put the chain onto the smallest chainring and biggest cog on the cassette. Screw the barrel adjuster all the way in and then unscrew it a couple of turns. Release the cable retaining bolt.
STEP 2: CHECK THE POSITION OF THE DERAILLEUR
Look at the derailleur from above. Are the plates that push the chain parallel to the chainrings? If not, loosen the clamp that hold the derailleur on the frame and align it.
STEP 3: ADJUST THE LIMIT SCREW
Adjust the limit screw so that chain is in the middle between the derailleur plates.
STEP 4: MOVE CHAIN ONTO THE BIGGEST CHAINRING
Use your hand to move the derailleur and push the chain onto the biggest chainring by turning the pedals. If the derailleur can push the chain too far, adjust the limit screw.
STEP 5: MOVE CHAIN ONTO THE SMALLEST CHAINRING
Gently release the derailleur and move the chain back onto the smallest chainring. Tighten the cable retaining bolt. Shift between the smallest chainring and the next largest chainring. If the chain falls between the smallest chainring and frame when shifting down, adjust the limit screw.
STEP 6: ADJUST THE SLACK IN THE CABLE
Release the retaining bolt and pull out and slack in the cable before tightening it again. Shift into one of the middle cogs on the cassette. Shift between the chainrings. If the chain gets pushed too far off the big chainring, adjust the limit screw. Take up any cable slack again.
STEP 7: FINE TUNE THE GEARS
If shifting onto a bigger chainring is slow, unscrew the barrel adjuster half a turn. If shifting onto smaller chainrings is slow, tighten the barrel adjuster.
Photo by istockphoto.com/portfolio/kdshutterman
EXTRA TIPS FOR ADJUSTING GEARS
If you find that you just cannot get the indexing right or the chain will not shift smoothly onto certain cogs, there could be a couple of things getting in the way.
1. WORN OR DIRTY OUTER CABLE
If the inside of the outer cable is full of dirt, worn away or rusted, this will create friction, preventing the inner cable from moving freely. If shifting into smaller cogs is slow, this could be the cause.
2. BENT DERAILLEUR HANGER
This is a metal plate that holds the derailleur on the frame. It is designed to bend or even snap under pressure, so that the derailleur or frame does not have to. Although annoying when it does happen, it is cheaper to replace.
A bent hanger will not hold the derailleur in the right position to shift gears correctly. You may be able to bend it back yourself but it is best to get a shop to attempt this or just buy a new hanger.
VIDEO: HOW TO REPLACE A BENT DERAILLEUR HANGER
3. WORN CHAIN, CASSETTE OR CHAINRINGS (OR ALL THREE!)
If your chain is skipping and jumping, it is probably worn out. Ideally, you replace your chain before this happens as a worn chain will grind away at the teeth on the cassette and chainrings, preventing a new chain engaging properly.
If this happens, you will need to replace all three. You may also want to invest in a chain measuring tool so you will know in the future when to replace the chain and not have the extra costs of replacing the other parts too. Check out this article about bike chain wear on Bike Radar to learn more.