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Bike Chain Keeps Falling Off. Help!

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There’s nothing worse than when you’re riding along and your chain keeps dropping off.

There are many reasons that can cause your bike chain to fall off, so we’ve made a list of some of them with a few tips on how to fix the problems.

7 Reasons Why Your Bike Chain Keeps Falling Off (and how to fix it!)

1. Chain is worn or damaged

Like most things, your chain can wear out over time, which can cause it to fall off.

If your chain isn’t worn out, it could be that it’s been damaged.

This can happen due to being poorly stored, causing the chain to rust.

Or the chain has been bent from a bump in the road or during storage or transportation.

How To Fix It:

If your chain is worn out, the chain will probably need to be replaced.

Make sure you choose the correct chain for your particular bike and you’ll probably need a chain tool.

Read more: How much are bike chains?

If your chain has a bend in it, you might be able to get it out by removing the link that has the bend.

You’ll need a chain tool to do this.

Removing one link will usually mean you can still keep the chain on your bike.

If you need to remove more than one link, the chain might then be too short.

2. Derailleur or cassette is worn out

Because the derailleur is an important and often heavily used component of your drivetrain, helping to shift the chain into the correct gear,  it can become worn out over time and especially through frequent use.

The teeth on the cassette can become worn with the frequent moving of the chain.

This can mean the chain links are not able to catch onto the teeth on the cassette, which can lead to the chain slipping off.

How To Fix It:

You may need to replace your derailleur.

You’ll need allen keys, pliers, a chain tool and a Phillips screwdriver.

You may also need to replace your cassette.

You’ll need a chain whip or vise whip, a lock ring tool, degreaser, and grease.

3. Chain is stretched or too long

If you recently fitted a new chain to your bike and it still falls off, it may be that the chain is too long for your drivetrain.

You can possibly remove links from the chain if you need to.

However, if you have a newly fitted chain it could also mean that the chain may not be compatible with your particular drivetrain.

If the chain is not new then it may have become stretched.

While the chain doesn’t actually stretch, it can loosen, making it longer, which can lead to a dropped chain.

Read more: How to shorten a bike chain

How To Fix It:

You can check your chain using a chain wear indicator tool.

This attaches into the links of your chain and tells you the percentage of wear, usually 0.5% and 0.75%.

If it’s 0.5% or greater, this usually means your chain needs to be replaced.

chain indicator tool fits inside chain meaning it needs to be replacedPin

4. Hitting Bumps Hard

The impact of hitting a curb or pothole, or going over a huge bump on an off-road trail, can all cause your chain to come loose and fall off.

How To Fix It:

Apart from avoiding hard bumps and crashes, you may be able to install a chain guide.

But chain guides are not compatible with all bikes.

5. Chain is dirty or clogged

Dirt and grease can build up in your chain and other bike components which can make your chain lose its grip on the teeth of the cassette.

This means it can be easier for your chain to drop during gear shifts or if you hit bumps in the road.

How To Fix It:

Clean your chain using a chain cleaner tool and a bike degreaser.

This can help to get all the dirt and grime out of the chain links.

You can also finish off with a bike lubricant to keep your gears shifting smoothly and this also can help to protect the chain.

6. Rear derailleur is misaligned

If your rear derailleur is out of alignment then this can cause your chain to drop off.

It can also mean your gear changes are noisier than they should be because the derailleur is possibly not in the center of the gear.

So each time you shift gears, the chain may not be fully aligned with the cogs.

How To Fix It:

You can check the derailleur yourself, usually with your bike upside down.

You should shift between the gears while you spin the pedals to check that it’s aligned.

You may need to tighten or loosen the screws, labeled H and L (for high and low), depending on the type of adjustment that you need to do to correct the problem.

7. Cross chain cycling

Cross chain cycling, or cross chaining, is when you ride with your chain on the biggest ring at both the front and the back cassettes.

Or, similarly, with the chain on the smallest ring at the front and back.

This can cause the chain to sit at an awkward angle, which can mean the chain drops.

Riding cross chained can also lead to stress on the chain, as well as damage to other components of your drivetrain.

How To Fix It:

Use a different combination of gears. Correspond the gears at the front with the ones at the back.

So if you’re on the middle ring at the front, opt for one of the middle rings at the back.

If you’re on the largest ring at the front, have your chain on the smallest one at the rear.

Drop It Like It’s Hot: Conclusion

Hopefully, you’ve identified the issue that’s causing your bike chain to fall off and can now have a go at fixing it, and potentially prevent it from happening in the future.

Let us know your thoughts and maybe you have some tips of your own that you’d like to share.

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Glenn Harper
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When Glenn isn't writing for BikePush, he can often be found cycling on his local rural roads. If he can help you benefit from bicycling in some small way, He’ll consider it a win.

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