Why Your Bike Chain Keeps Falling Off and What To Do About It

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You think you’re going for a smooth ride, but then your bike chain falls off. Not only is this annoying, but if the bike chain keeps falling off in traffic, you could get into a serious accident. The chain could fall off the front or off the rear wheel.

Man adjusting bike chain that keeps falling off

Why Your Bike Chain Keeps Falling Off

When a chain drop happens, or when your bike chain keeps falling off, usually it’s a problem with the drivetrain system, including the drivetrain bolts, jockey wheel, or the limit screws on the rear derailleurs. There could also be a problem with the chain tension, which naturally decreases as you ride your bike.

Fixing a problem with the bicycle chain is usually easy enough with some simple tools, such as a chain tool. But many parts could be causing the stiff link or loose chain, so here’s a guide to help you troubleshoot which part is the culprit:

Check the Chain

One of the primary culprits of a chain drop is the chain itself. As the chain naturally stretches due to wear and tear, eventually it will no longer fit properly on the entire cassette and will be prone to falling off.

How To Identify if the Chain Is the Issue

A problem with the chain tension is one of the most common culprits for the chain falling off. The chain is likely the cause of your problem if the chain gets loose when you pedal hard, or if it usually falls out of the front chainrings.

Check the chain’s flexibility and movement. If it has a stiff link, does not bend easily, or gums up in certain places when you try to pedal the bike, that’s a sign that it is not as flexible anymore and should probably be replaced. Pay special attention to how the chain passes over the jockey wheel, which is the pulley that helps the derailleur shift gears. A stiff link will have trouble making a tight chain and is an indication that your chain should be replaced.

If it’s been some time since you replaced your chain, then that’s probably the reason why you’re having a problem. The majority of bicycle chains need to be replaced every 1,000 to 2,000 miles because the links get stretched out with wear and tear. If you’re not sure, check the chain health with a chain tool or ruler. (It’s always a good idea to keep a chain tool handy.)

The Park Tool CC 3.2 Chain Wear Indicator is an example of a chain checker tool that makes it very easy to determine if your chain needs replacing:

Park Tool CC-3.2 Chain Checker Check availability

Here’s a short video that shows you how to use the CC 3.2 chain checker:

How To Fix an Issue With Your Chain

If your bike chain keeps falling off, you can try to resolve the chain tension by tightening the derailleurs.

If it’s been a while since you replaced the bike chain, it’s better to just go to a bike shop for a new one. A bike chain replacement is inexpensive, and it’s better to replace a worn-out chain anyway. You can also get help from a bike shop mechanic if you don’t know how to replace the chain yourself.

If you plan to replace the chain yourself, make sure you know how to find the master link on your bike chain.

You should also be sure that you are using the correct chain to work with your drivetrain system. Check system compatibilities before buying a new chain. If your chain is too long, that could also cause problems with the tension.

Check the Drivetrain System

The drivetrain system consists of all the drivetrain components that interact with the chain to move the bike along. This includes the derailleurs, pedals, cassettes, and more. A problem with the drivetrain system can affect how the chain sits along the bike.

Check the Bolts

The drivetrain system consists of countless moving parts that can easily get knocked loose during your ride. Simply tightening the bolts can help resolve the issue of your chain falling off.

First, check the drivetrain bolts. These bolts, sometimes called the drive shaft bolts, hold the drive shaft and the axles together. If they’ve been knocked loose, tightening them will help stop the chain from falling off.

The derailleur, which shifts the chain into gears, could also be loose. Check your front or rear derailleurs and adjust the limit screws (there will usually be two of these: one marked H for high and one marked L for low). Adjust the H screw if your chain comes off the outside of your chainset. Adjust the L screw if your chain comes off the inside of the chainset.

Check the Cogs

As mentioned above, the drivetrain system contains many moving parts, all of which get damaged through wear and tear. Check all the parts for damage or dents, particularly the cogs along the cassette and the chainrings.

If you’ve been rattling around on an old chain for too long, or have put your drivetrain system through too much, then the cogs may be too worn down and you will need to replace the cassette and a few other parts. Just replacing the chain won’t help your problem in this situation because there won’t be the right cogs in place to hold the chain in place.

Adjusting Your Setup

If you’ve tried troubleshooting for problems with your chain and the drivetrain system but you’re still struggling with chain drop, then it may be time to change your bike setup to protect the chain.

This is particularly important if you are going mountain biking or regularly riding over rough terrain. No matter how good your chain and drivetrain bolts are, they won’t hold up to so much jostling without some help.

Get a Better Derailleur

Bicycle derailleur that needs to be adjusted to solve issue with bike chain that keeps falling off
A rear derailleur.

High-end brands, such as Shimano, now manufacture high-tension derailleurs that go on the rear wheels of mountain bikes to hold chains in place. The higher tension, combined with a narrow-wide chainring, is the optimal setup for preventing mountain bike chain drops when mountain biking over bumpy roads.

Adding a Chain Catcher or Stabilizer

If you have consistent problems with the chain falling off, it might be worth investing in a chain catcher. A chain catcher is a tool that attaches to the front mech bolt and prevents the chain from slipping inward. Some front derailleurs come with an attached chain catcher. You can also buy the attachment separately.

If you have a rear derailleur, you should invest in a stabilizer. Stabilizers are the parts of a rear derailleur that help keep the chain in place.

Sometimes the stabilizer switches off without a cyclist noticing, so if you have one, make sure that yours is on.

Adjust Your Riding Style

Sometimes the problem may have to do with the way you ride. If you are putting too much pressure on your chain as you switch gears, that could be causing it to slip. Try to pedal with less intensity when switching gears or chainrings as that makes it more likely for the chain to stay in place.

Adjusting your riding style is an imperfect solution, but it can help prevent the chain from slipping before you have time to fix the issue.

Fixing a Faulty Bike Chain

Hopefully this article can help you make the necessary adjustments to keep your bike chain where it belongs. Common reasons for why a chain keeps falling off include the chain itself (if it is loose or damaged) or an issue with the drivetrain system. If your bike chain keeps falling off, consider adding parts to your setup that help keep it in place, such as a stabilizer or a chain catcher.

If you notice that your bike chain is rusting, see our post on how to clean a rusty bike chain.

And if your bike chain is skipping gears, check out our post on how to fix a bike chain that’s skipping.