Why Does My Bike Chain Keep Falling Off?

When a bike chain falls off, most cyclists rush to reattach it. But does that solve anything? Probably not, and that’s why you’ve to ask, ‘why does my bike chain keep falling off?’

Most bike chains fall off because they are either loose, stretched, too long, clogged, worn out, or just the wrong size. Sometimes, however, the problem might be a misaligned or dirty, or worn-out drivetrain. At other times, the chain may keep falling off because you are pedaling hard or back-pedaling.

I’m going to explain all these possible scenarios and suggest a quick fix for each. Hopefully, you’ll learn to solve the issue behind your bike chain falling off.

Let’s begin:

why does my bike chain keep falling off

Why Does My Bike Chain Keep Falling Off? 10 Possible Reasons And Fixes

Let’s look at ten possible reasons why your bike chain cannot stop slipping off and what you can do to stop that.

1. The Chain Might Be Clogged And Dirty

You cannot expect your bike chain not to slip off if it’s clogged with either grime, dirt, or grease. That’s why proper cleaning of the bike chain with a chain cleaning oil is recommendable.

The Fix

Clean your chain correctly to ensure you get rid of the grime, dirt, and extra grease. Consider using a powerful chain cleaner like the Finish Line 1-Step Bicycle Chain Cleaner, which doubles up as a chain lubricant.

2. The Chain Might Be Loose

If the chain is loose, you cannot expect it to stay in position. It’ll fall off.

So, before riding your bicycle, see if the chain has the correct tension. If not, then you’ve to tighten it.

The Fix

Here’s how to tighten bicycle chain:

  • First, loosen the tight bolts that hold your bike’s rear-wheel
  • Then pull back the rear tire to tighten the chain
  • Once you get the correct chain tension, re-tighten the bolts

If this fix doesn’t work, it might be time to replace your bike chain.

3. The Chain Might Be Long

If your bike chain is longer, then it’s likely to slip off. So, before you can replace your bike chain, you’ve to ensure it’s the right size.

The Fix

For a long bike chain, you’ve no choice but to replace it. Find the best bike chain online.

Remember, however, that you have to get the right size this time around. It should be the same size as the original bike chain.

If you are not sure, take your bike to the local bike repair shop, and they’ll advise you appropriately.

How To Fix A Bike Chain That Keeps Falling Off

4. The Chainring Might Be Bent

If the chainring or its tooth gets bent after knocking something for whatever reason, the chances are that the chain will slip off when you cycle.

The Fix

If you’ve recently suffered an accident with your bike, check the chainring and its teeth to ensure they are not bent.

If they are, then straighten them. You can use a regular wrench or a chain-link straightener to straighten the chainring.

5. The Drivetrain Might Be Dirty

If either the derailleur or any other part of the drivetrain is clogged with dirt, the chain will slip off. So, you also have to clean it.

The Fix

You can use a brush to get rid of grime and dirt and a degreaser or soapy hot water to eliminate excess grease.

For a more comfortable cleaning experience, use the Park Tool CG 2.4 Bicycle Chain & Drivetrain Cleaning Kit. This kit features a cleaning brush, degreaser, and scrubber.

6. The Derailleur Might Be Misaligned

A poorly aligned front or back derailleur will cause a shift in the bike chain position, making it slip off when cycling.

The other thing that a misaligned derailleur will do is that it’ll produce some noise when shifting.

The Fix

Here are the steps for readjusting the rear derailleur:

  • Shift the chain onto the biggest front chainring and the smallest rear cog
  • Turn the barrel adjuster counter-clockwise to loosen it
  • Tighten the H-screw counter-clockwise by a half-turn, then clockwise by a quarter turn
  • Retighten (clockwise) the barrel adjuster
  • Shift to the second biggest front chainring and the second biggest rear cog to adjust the L-screw
  • half-turn the L-screw to tighten it and then loosen it by a quarter turn

And if it’s the front derailleur that you’ve to reposition, here is a guide on adjusting the front derailleur.

7. The Drivetrain Might Be Worn Out

Even if you replace the chain and the rest of the drivetrain is worn out, it’ll all be in vain.

You’ve to check the drivetrain’s components (other than the chain) to ensure they are not worn out. That includes the chainring, derailleur, cog, and cassette.

The Fix

You don’t have to think about how to fix bicycle chain if it’s a case of a worn-out drivetrain. So, replace the drivetrain components that are worn out.

Check for signs of wear before doing it but if you are not sure, take the bike to a repair expert.

bike chain keeps falling off

8. The Chain Might Be The Wrong Size

If you just replaced your bike chain and it just can’t stop falling off, you probably bought the wrong size. That’s if there’s no other issue affecting the drivetrain.

The Fix

You’ll have to replace the bike chain but ensure you get the size right this time around.

Remember, the correct chain shouldn’t be loose or too tight.

9. The Chain Might Be Stretched

A chain stretch is sometimes regarded as chain wear, although it’s ordinarily a case of the chain growing in length.

Whether you call it chain wear or a lengthy chain, it’s not a good thing as it might be the reason why your bike chain keeps falling off.

The Fix

Check for chain stretch using a chain wear checker like the Park Tool CC-2 Chain Checker. It’ll show you the degree of chain stretch/wear.

Once you confirm a chain stretch, replace your bike chain.

10. The Chain Might Be Worn Out

No matter the effort you put into fixing your bike chain, it might be all in vain if the chain is already worn out.

Remember, the bike chain has an expiry, what we call a mileage. In most cases, the average lifespan of bike chains is about 2 000-3 000 miles, but it can be more with proper maintenance.

Once you go past the mileage, you must replace the chain, lest you’ll have a hard time cycling.

The Fix

Once you notice signs of wear on the chain or it exceeds its mileage, replace it immediately. You can use a chain wear checker to check for signs of wear.

Others Possible Reasons for a Bike Chain That Keep Falling Off

Also, your bike chain may be falling off because of any of these reasons:

  • You pedal so hard – If you pedal with a lot of force, you may force the chain off the chainring. If that’s the case, reattach the chain and pedal much gentler.
  • You might have been back-pedaling – If you’ve been back-pedaling, there’s always the chance that your bike chain will slip off the chainring. That’ shouldn’t alarm you, however, as it’s correctible by reattaching the chain.
  • The derailleur hanger might be bent – If the derailleur hanger is bent, the chain will fall off. So, use a wrench to straighten it. Do it gently not to break the hanger.
  • It might be due to a stiff link in the bike chain – A rigid link will make it hard for the chain to stay in position. In most cases, oiling the chain will fix the issue. But if it doesn’t work, then fold and bend the links.
  • Sprockets may be damaged – The sprockets may get damaged due to frequent rolling. If they do, then the chain may fall off. In that case, you’ll need to replace the sprockets.
  • Sprockets may be misaligned – The sprockets may also cause the chain to fall off if they are out of place. So, adjust them properly to fix the problem.
Why Does My Bike Chain Keep Falling Off

Quick Fixes – How To Fix A Bike Chain That Keeps Falling Off

Here are solutions to fixing a bike chain that keeps falling off:

Option 1 – Reattach The Fallen Chain

Immediately after your bike chain has fallen off, consider reattaching it. That’s if it’s nothing serious.

Here are the steps for doing it:

  • Turn your bicycle upside down to allow you to fix the chain more comfortably. If you have a bike stand, you can hang your bike there.
  • Loosen the chain by pushing the rear derailleur towards the bike handles.
  • Now use one hand to return the chain to the rear gear.
  • Slowly back-pedal with your hand to slip the chain back in position.

Option 2 – Use A Chain Catcher

You can prevent your bike chain from slipping off the chainring by using a chain catcher. It acts as an arm barrier that holds the chain in place when cycling.

One excellent chain catcher is the K-Edge Pro Braze-On Chain Catcher.

Option 3 – Add A Chain Guide

You can also stop a bike chain from coming off the chainring using a chain guide, also known as a chain tensioner. It’ll keep your bike chain in place, and this is more important when descending.

You can check out the MRP AMg V2 Alloy Chain Guide if you are looking for the best chain guide. It’s lightweight and suits a wide range of chainring sizes.

Also Read: Why Does My BMX Chain Keep Snapping?

Closing Thought:

So, why does my bike chain keep falling off? I hope I’ve answered this question comprehensively. You can use the tips that I’ve shared to fix your bike chain problem.