Most of us do not think much if the bike chain falls off because it is normal if it happens once in a few weeks. It is a nightmare that the chain keeps falling off bike. You cannot enjoy an outdoor adventure if you have to stop every few minutes and fix back the chain. It is better to learn about the bike chain working mechanism to diagnose and solve the problem.

How Does the Bike Chain Works?

The bike chain works with the help of a chainring, one or two derailleurs, a cassette, and two crank pedals. When you want to move the bike forward, you need to put your feet on the pedals and force the crank to move. As the chain moves, the bike chain will move with it. The holes in the bike chain fit perfectly with the teeth on the metal of the chainring. The chainring rotation forces the chain to come from the upper side of the chainring and move towards the lower side. The cassette of the wheel takes the force from the bike chain. The bike chain delivers power by entering from the downside and exiting from the upper side. This continuous motion allows the rotation of the rear wheel. There is a derailleur on the rear wheel side to move the chain between different rings of the cassette.

Top Possible Reasons of Bike Chain Keeps Falling Off

To understand the reasons for the malfunctioning bike chain, you need to learn about the different reasons causing it. There can be hundreds of reasons for the bike chain issues. We have compiled the most frequent causes that can cause the problem. Once you learn about these issues, troubleshooting will become a piece of cake.

Dirty Chain With Clogged Holes

A dirty chain is one of the minor problems for the chain falling off. When driving on a dirt road, some dirt attaches to the chain. These dirt and stone particles can clog the chainrings. The chain only needs a few clogged openings to cause the falling-off issues. When the clogged hole comes on the chainring, they do not allow the chainring teeth to fit in. These minor alignment issues will force the chain to come off the chainring or cassette.

Unsuitable Chain Length

The technician will adjust the chain length to fit it perfectly when he installs it. As time passes, stretching forces dominate the chain. It can affect the chain length. A stretched chain will not come from the chainring to the cassette in a straight line. It will come in a curved line. You can identify this issue easily as the chain from a U-like shape as it comes from the chainring to the cassette from the lower side.

Uneven Chainring

If your chain is falling off after the bike fell, it can be due to the uneven chainring. When the chainring does not rotate in a straight line, it will produce a sideway vibration in the bike chain. You may not notice this vibration when you are paddling the cycle. You need to get off the cycle and rotate the pedal with your hand. If the chainring is uneven, you will notice the vibration in the chain.

Cassette Damage

Diagnosing the cassette damage is harder than finding issues with the chainring. You need to check all the rings of the cassette to find out which ring is causing the issue. You can do it by changing the gears. You need to note the number of the gears that are causing the chain to fall off. Sometimes all of the rings can have alignment issues after the bike fell. You can decide if you need a cassette repair or replacement based on this diagnosis.

Derailleurs Misalignment

If you are using an old bike you can face issues with the derailleurs. The problem is more prominent with the bikes with many gears and shifters. You can adjust the gear from the shifter on the bike handle. If the chain falls off when you are changing the gears, the problem can be with this part. You can shift gears many times to note which location causes the chain to fall off. You can use this process to diagnose the problems of the derailleurs and the cassette.

Wrong Size of Chain

It can be surprising to know that your bike has the wrong chain size. Length is not the only parameter you have to consider when choosing the bike chain. You need to choose the accurate width also. If you do not install the correct chain, it may come off often. You may not notice the problem when the chain is new as it will handle the chainring and the cassette at the start. As the chain gets a little old, the falling-off issue gets worse. You can check the internet to find out about the chain size for your bike. It is better to consult an expert to find an accurate chain size.

Worn out Chain

The chain holes can become uneven after using them for a few years. You can observe the signs of wear on the bike chain when you look closely. You need to look for scratches on the chain and inside the holes. If there are some scratches on a specific chain part, you can mark it. If the chain falls off from the same part, you'll know what you are looking for.

How to Fix A Bike Chain That Keeps Falling Off

After reading the causes of the chain falling off, you should know why it is happening and how to diagnose it. It is possible to solve the issue if you diagnose it accurately. You can use some of the ways to get rid of the issue. The solution can be as simple as cleaning the chain or as complicated as changing many drivetrain parts. We will focus on the things that you can do by yourself. You can consult a professional technician if things do not work out.

Chain Cleaning

Cleaning the chain is a simple way to stop the chain from falling off. You can get a brush and a thin screwdriver for this purpose. You can start by cleaning the chain with a brush. Once it is clean, you can remove the small stones from the chain holes using the thin screwdriver. It is better to clean the chain before you do any other steps. Learn more details about how to clean the ebike chain here.

Rear Wheel Adjustment

If the bike chain has stretched a little, you can adjust it by changing the rear wheel position. You can loosen the bolt of the rear wheel and pull it backward. Once the chain is tight, you can tighten the bold to fix the rear wheel in place. It will help you solve the issue without replacing the chain.

Correct the Chainring Wheel Uneven Surface

You can take a wrench to correct the uneven chainring surface. You need to look for teeth that are not aligned. You can use the wrench to correct their alignment. If the chainring has a minor bend, you can also correct it using a bigger wrench. It is better to remove the chainring before you try to adjust it. It will protect other parts from damage.

Correct Cassette Alignment

You can correct the cassette alignment using the wrench also. You can also use the pliers for the smaller gears. It will take more time to diagnose the issue and correct it. If you have an issue with the cassette, it is better to find a professional to help you. They have tools to check the alignment.

Derailleurs Adjustment Correction

There are two ways to correct the derailleurs adjustment. You need to find the limit screw preventing the chain from falling off. You need to adjust this screw to correct the chain delivery to the cassette and the chainring. You can also check the adjustment of the metal piece that attaches the derailleurs to the bike frame. You have to adjust that also in the newer model bikes.

Bike Chain Replacement

If the chain is worn and nothing else is working to solve the issue of the chain falling off, you need to replace the chain. It is essential to find a professional with extensive bike knowledge. He will help you find the chain with suitable width and length. He will adjust the chain perfectly to avoid future problems. If you are a bike expert, you can do it by yourself also. Many articles on the internet can guide you about chain replacement.


The bike chain is an essential part of the drivetrain system. The bike will not run without the chain. A malfunction in some parts of the bike can lead to the chain falling off. You can diagnose the issue with the instructions in this article. It is better to solve some problems by yourself. If you do not understand something, getting help from a professional is the best idea. You can also look for video tutorials and articles online to help you solve this issue.

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