If a chain keeps coming off bike then this is a sign that there might be an issue with your gears, chain or the wheel. In this article we are going to look at the reasons why the chain keeps coming off and how to solve it.
Chain keeps coming off bike with gears
– Out of alignment limit screws. If the chain comes off while changing gears on the extreme cogs either at the front or the rear then it is most likely to be caused by badly set-up limit screws. Adjusting the limit screws will solve the problem. We have a great video here that will guide you through this task.
– Bent hanger. If the chain comes off while changing the gears to the biggest sprocket at the back then this could be an indication of a bent hanger. This can happen if the bike is knocked or falls over. Because it is really hard without a specialist tool to see if the hanger is bent, check the front of your derailleur for any scratches as this could indicate hanger damage. If this is the case, replacing a bent aluminium hanger is the best solution as trying to straighten it can cause it to break.
– Seized freewheeling mechanism. If the freewheeling mechanism has developed resistance, then while pedalling backwards or freewheeling the chain can slacken and come off. if it is a cassette wheel you will need replace the freehub body or the wheel. If it’s a freewheel you will need to replace the unit. We have a great video here if you need help with this task.
Putting the chain back on a derailleur bike
We suggest wearing gloves for this task as the chain will probably be dirty.
When it comes off the largest front sprocket.
- Push the arm of the rear derailleur forward to slacken the chain.
- While holding the arm, feed the the chain onto the chainring starting at the bottom.
- When it’s near the derailleur, release the rear derailleur arm and move the pedal backwards.
When it comes off the smallest front sprocket.
- Check if the chain is wedged between the bottom bracket and crankset. If it is, then while pulling the chain, move the crank backwards and forwards until it releases.
- Now push the arm of the rear derailleur forward to slacken the chain.
- While holding the arm, feed the the chain onto the chainring starting at the bottom.
- When it’s near the derailleur, release the rear derailleur arm and move the pedal backwards.
When it comes off the smallest rear sprocket.
- First click the shifter to the next gear so that the chain doesn’t fall off again.
- Push the derailleur body backwards.
- While holding the derailleur, grab the chain above the top jockey wheel and lift it clear.
- If the chain is wedged between the frame and the cogs, you may need to remove the wheel to release it.
- Place the chain on the sprocket.
- Lift the rear wheel and pedal forward so that the chain can jump onto the correct gear.
When it comes off the largest rear sprocket.
- First click the shifter to the next gear so that the chain doesn’t fall off again.
- Push the derailleur body backwards.
- While holding the derailleur, grab the chain above the top jockey wheel and lift it clear.
- If the chain is wedged and you can’t get it out, you may need to seek help to release it as the cassette or freewheel might have to be removed.
- Place the chain on the sprocket, lift the rear wheel and pedal forward so that the chain can jump onto the correct gear.
Chain keeps coming off bike without gears
Loose chain. If the chain comes off while pedalling it is probably because it isn’t tensioned enough. This can happen either because the chain wears and stretches over time or because the wheel isn’t tight and can move enough to loosen the chain Use the chain checking tool and if the chain is worn then replace and tension it. If the chain is not worn then just re-tension it. 
We have a great article here if you’re not sure how to replace a chain.
You can also watch our video tutorial here:
If you need to tension your chain then in our article here we have explained how to do this step-by-step.
You can also watch our video tutorial here:
If the problem persists, then it could be that the thread or the serrations on the wheel nuts are worn. If this is the case, then the wheel nuts will have to be replaced.
Putting the chain back on a non-derailleur bike
- First put the chain onto the rear cog.
- Now put the chain onto the top of the chainring.
- Lift the rear wheel and pedal forward.
Watch our video tutorial on how to fix a chain drop here:
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