If your bike is having difficulty shifting, staying moving, or its chain is falling off, you should adjust its gears. The derailleurs are devices that allow you to change gears, pushing and pulling the chain at different speeds each time you make a change. While this process may seem a bit daunting, adjusting a bike's gear won't be difficult if you're patient and have a few tricks up your sleeve.
Steps
Method 1 of 2: Adjust the Gear
Step 1. Raise the bike off the ground on a stand
You should be able to turn the wheels freely without the bike moving. The best way to do this is with the use of a bike rack. If you don't have one, check to see if a local bike shop or outdoor store hosts a "maintenance night," where you pay a small fee to access all of their tools overnight.
- You can also turn the bike upside down, resting it on the seat and the handlebars. However, if you do, you will need to reverse the direction in which you rotate the pieces in the following instructions.
- You can also hang the nose of the seat in a tree notch or low hanging joist.
Step 2. Locate the derailleurs
These elements are the machines that physically change gears and hold the chain in place. There is one on the rear wheel connected to the cassette (the gear collection) and a smaller one near the pedals. Check that there is nothing on the derailleurs or gears (such as leaves, sticks, or mud) and wipe them off with a damp cloth.
- The rear derailleur is the most complex machine, consisting of the derailleur itself, an arm, and 1 or 2 smaller gears through which the chain is threaded. A cable pulls this arm back and forth, allowing the chain to change gears.
- The front derailleur is attached to the bike frame and consists of a spring and two “plates” (or small metal walls that force the chain to stay in one gear at a time).
Step 3. Diagnose shift problems by testing each gear
With one hand, lightly pedal the bike and shift one gear per click, starting with each gear on the rear derailleur. Go up each gear once and down each gear once. Look at the areas where the gears are having trouble shifting (where the chain slips off the gear, or where you need to manipulate twice to get the bike to shift gears).
While testing one derailleur, put the other in mid gear. For example, if you are testing the rear derailleur and you have 3 speeds at the front, you should leave the front derailleur on the center ring at all times. This will prevent the chain from stretching
Step 4. Find the cable adjusters
Follow the cables leading to the derailleurs to find the adjusters, which look like little nuts or barrels that surround the cables. There are probably two for each cable: one on the end of the derailleur and one on the handlebar. These elements make small adjustments to the derailleur cables, allowing you to make subtle changes while shifting gears.
Step 5. Shift into “problem gear”
While pedaling the bike with one hand, move the gears up until you detect a problem (for example, the chain won't shift, has trouble staying in gear, or skips a gear). Stop shifting when you spot a problem, but keep the bike in that gear.
Step 6. Loosen the cable adjuster if the chain does not shift down
If you have trouble shifting gears as you go down (the lower gears are closer to the wheel), you should loosen the cable adjuster by turning it counterclockwise. Turn the adjuster slowly, until the chain drops into the correct gear.
- You should always work slowly, adjusting a quarter turn at a time at most.
- Think of this as turning the adjuster the way you want the chain to move. Rotate it towards the bike to make the chain move towards it.
- Avoid loosening the adjuster too much, as it may come off the derailleur. If you need to make a big adjustment, screw the adjustment into the derailleur, shift to the lowest gear, loosen the set bolt and pull the cable by hand.
Step 7. Secure the cable adjuster if the chain does not shift “up”
If the bike is having difficulty operating and is high above the gears (away from the bike), you should secure the cable adjuster by turning it clockwise. If everything is correct, the chain will naturally shift into the correct gear on its own.
Think of this as turning the adjuster the way you want the chain to move. Rotate it away from the bike to make the chain move away from it
Step 8. Return to low gear and fully back up and down
Once you have properly adjusted the problems, cycle through each gear again to ensure the derailleur can successfully traverse each gear.
The goal is for the chain to flow smoothly from gear to gear each time you shift
Step 9. Take a short practice trip to spot any other problems
Sometimes the bike will behave differently under your weight. You can ride the bike in a parking lot or driveway and shift into any gear. If you find a problem, you should adjust the cables accordingly.
Method 2 of 2: Repair a Slipping or Limited Chain
Step 1. Raise the bike off the ground on a stand
You should be able to turn the wheels freely without the bike moving. The best way to do this is with the use of a bike rack. If you don't have one, check to see if a local bike shop or outdoor store hosts a "maintenance night," where you pay a small fee to access all of their tools overnight.
You can also turn the bike upside down, resting it on the seat and the handlebars. However, if you do, you will need to reverse the direction in which you rotate the pieces in the following instructions
Step 2. Shift into the lowest gear
This is the gear furthest from the bike on the rear derailleur, and the small gear closest to the bike on the front derailleur.
- Shift the gear in which no you're working somewhere in between.
Step 3. Unscrew the bolt that holds the cable in place
This element is at the end of the cable that runs from the handlebar to the derailleur. A small bolt holds the cable in place, keeping it snug. Use an Allen wrench to unscrew the bolt and free the end of the cable.
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Advanced note:
you will notice that if you pedal the bike, the chain will slide towards the lowest ring without your help. This is because the derailleurs work by adjusting the cable to keep the chain in place. Similarly, you can change gears by hand by pulling the cable.
Step 4. Locate the derailleur's “limit bolts”
To prevent the chain from slipping, the derailleur is contained in the small area between the gears. There are two small screws that hold the derailleur in place, located side by side on the top (front) or rear of the derailleur.
- the screw on the left, often labeled with an “H”, which limits the height of the chain and affects the external gears
- the bolt on the right, often labeled with an "L", which limits how low the chain can extend and affects the internal gears
Step 5. Tighten the bolts to prevent the chain from falling off
If the chain falls near the outer gears of the front derailleur, you should adjust the H bolt to limit it. If the chain falls closer to the wheel, you should adjust screw L.
You can check your bike manual if the H and L screws are not clearly labeled
Step 6. Use your hand to push the rear derailleur towards the inside of the bike as far as you can
If the derailleur pushes too far, the chain will fall off the gears onto the wheel. Another alternative is that it does not push enough and the chain does not reach all the gears. You can then adjust the limit bolts to move the derailleur (and really watch it move).
- Adjust the low limit screw if the chain extends too far. This will prevent the derailleur from moving too far to the left.
- Loosen the low limit screw if you can't change to every gear. This will allow the derailleur to move further in.
Step 7. Adjust the front derailleur so its plates sit on both sides of the chain
With the chain on the smallest gear, adjust or loosen the low limit screw so that the chain does not touch the derailleur plate.
Pull 2-3 ml of space on each side of the chain
Step 8. Screw the cable onto the derailleur
Shift back to the smaller gears and tighten the cable by hand. It doesn't have to be perfect, just be tight. Then screw the cable into place under the bolt on the derailleur that you removed it from.
Often times, you can spot a mark on the wire that indicates where it was previously screwed on
Step 9. Use the cable adjusters to adjust your gears correctly
Make sure the bike can comfortably move to and from each gear front and rear, and use the cable adjusters to make changes when necessary. You only need to change one gear per click.
Advice
- You should make changes slowly, as it will be easier to readjust them if you make a mistake.
- Take notes or photos of the bike before starting work if you have any questions about putting it back together.
- Clean and lubricate the chain regularly to avoid shifting problems and keep it running smoothly.