Skip to content

Why Your Bike Chain Keep Falling Off and How to Fix it

Why does my bike chain keep falling off ? That was the exact question my friend from way back asked last night while having a bikers hangout with other friends. Immediately it was asked, we all realized at one point or the other, we’ve individually experienced it. 

A bike chain keeps falling off is a normal occurrence but the moment it becomes frequent, then it is a problem that needs to be addressed. Some common reasons for your bike chain coming off intermittently are discussed below after some research.

There are various reasons that can cause the chain to keep coming off your bike. In this article, we will discuss these problems and how you can fix them. 

Why Does my Bike Chain Keep Falling Off ? 8 Possible  Reasons 

Be it a mountain bike or a regular bike, there are explainable reasons for the occurrence. Below, we will discuss the various reasons we know as well as how you can fix the problems. The reasons a cycle chain keeps coming off include:

  • Excessive chain angle
  • Using a wrong chain size
  • Incompatibility with the drivetrain
  • The chainring tooth is damaged or bent
  • The rear derailleur doesn’t fit into the alignment
  • Hard pedaling
  • The rear derailleur hanger is bent
  • The derailleur is dirty and needs to be cleaned

Excessive chain angle

Many cyclist are still not aware that cross-chain riding is bad. If you find yourself  under this category, you might as well be the major culprit for your chain coming off.

Engaging in cross-chain riding will over time cause a chain rub stress on the hardware. Eventually it will lead to the chain angle becoming slant.

Fixing this problem requires no extra effort other than you been aware of your gear usage each time you on a ride. 

Using a wrong chain size

New chains or fairly used chains are usally shorter in lenght than old ones. So if your chain keeps pulling off your bike, then the problem is certainly not becuase it is new. 

If the chain won’t fit, its probably becuase it has overslacked. All you have to do is to get the right chain measurment by measuring the old and new chains. Having determined  the lenght difference, obtain the right lenght by removing a couple of links from the longer chain.

Incompatibility with the drivetrain

Drivetrain incompatibility doesn’t just occur. Having been used over thousands of kilometers without being changed, worn-out is expected to occur.

So if you’ve been using your bike for a long time without changing the drivetrain, you might just be giving room to a chain pulling off sooner or later.

Under this condition, a full replacement is needed depending on your pocket size. You can as well replace the individual cogs.


The chainring tooth is damaged or bent

A damaged or bent chainring can be the cause of your mountain bike chain coming off. Most often, the cause of the damage is an accident or the bike hitting a hard surface with a ferocious force.

Why does my bike chain keep falling off?

If the damage to the chainring isn’t much, you can perform a quick DIY by using a wrench to bend the chainring back to its original position. If this doesn’t work, you might need to change the chainring completely.

The rear derailleur doesn’t fit into the alignment

Rear derailleurs are know to cause noisy shifts when not properly aligned. Apart from this, severe misalignment can also lead to chain drops. Before going on a ride, ensure that the rear derailleurs are proerly fixed to avoid an accident.

Hard pedaling

Were you hard-pedalling when your chain suddenly come off? While this is almost impossible, there are other remote causes that can cause the chain to come off while you’re pedalling hard. This can occur if the chain is worn out or not being the right lenght. 

The rear derailleur hanger is bent

It is possible that your rear derailleur is bent without you even realizing it. Always inspect it to be sure it fits peferctly. If bent, use a wrench to realign it to its orignal shape. 

The derailleur is dirty and needs to be cleaned

An extremely dirty derailleurs will never function well. However, you can prevent this by carrying out routine maintenance. Deep a brush in a degreaser and use it to brush off all builtup dirts the derailluers have attracted. 


A bike chain falling off isn’t a pleasant news. It is dangerous and can lead to accident if not fixed permanently. Before chains can come off, there are various causes. Some of the causes include, hitting a hard bump especially mountain bikes, overstretched chain, dirty derailluers etc. 

Immediately you noticed a slack chain, do not manage it. Fix it immeditely before other components of your bike are damanged as well.  



Leave a Reply

Your email address will not be published.