Having your bike chain fall off is a nuisance all cyclists will experience at some point.
Besides being irritating, it can also be dangerous – you could slip off the pedals if the chain comes off while you’re standing out of the saddle, or the sudden loss of power could leave you stranded in the middle of a busy junction!
It’s therefore vital to learn how to put a bike chain back on quickly and easily so you can get back in the saddle with minimal fuss.
It’s also important to understand the reasons why your bike chain might be falling off, and some quick fixes for a chain that’s falling off every time you hit the road!
In this guide, we’ll walk you through:
- How To Put A Bike Chain Back On In 4 Steps
- Why Does My Bike Chain Keep Falling Off? 5 Possible Causes And How To Fix Them
Ready to get riding again?
Let’s get started!
How To Put A Bike Chain Back On In 4 Steps
Step 1: Try To Get The Chain Back On While You’re Still Riding
The most common place for a bike chain to slip off is from the smallest of your chainrings (the front set of gears).
If this happens to your bike, there’s a chance you might be able to get the chain back on while you’re still moving.
While pedaling, shift your front derailleur into the position of the biggest chainring (the hardest gear). With a bit of luck, the derailleur will drag the chain just enough to catch on the teeth of the chainring, and it should pull itself back into place as you pedal.
This should always be your first response to your bike chain falling off at the front – it could save you having to stop at the side of the road at all!
Step 2: Check Whether The Chain Is Trapped Against The Frame
If that hasn’t done the trick, you’ll need to find a safe place to stop and get off the bike for a closer look.
You might find that the chain has trapped itself between the cassette (the rear set of gears) and the bike’s frame. If this is the case, you’ll need to loosen the rear wheel until there’s enough wiggle room to release the chain.
If your bike’s wheels have a quick-release mechanism, simply open the lever and turn it a few times until there’s enough space to pull the wheel out by a couple of centimeters. You should now be able to pull the chain free.
If you’re riding an older bike with hexagonal axle bolts instead of a quick release, the process is the same, but you may find that you need a wrench to loosen the rear wheel.
Whichever type of axle you’re using, always make sure you remember to tighten the wheel again before hitting the road!
Step 3: Push The Rear Derailleur Forward
Change gears to shift your derailleurs into position over the smallest chainring and the smallest sprocket of the cassette.
The rear derailleur on a bike is spring-loaded to keep the chain taught. Using your left hand, push the rear derailleur forward to create some slack in the chain. This will make it easier to ease the chain back into place and help prevent your fingers from getting pinched in the process!
Step 4: Lift The Chain Back Into Place
With the derailleur pushed forward, lift the slackened chain onto the smallest chainring first.
Once the front section of the chain is in place, pull the rear end over the smallest sprocket. With both sides of the chain back in position, you can now release the rear derailleur to bring back some tension.
With all these steps followed, you should be ready to get back on the road!
Why Does My Bike Chain Keep Falling Off? 5 Possible Causes And How To Fix Them
#1: Your Chain Is Worn Or Damaged
Like all bike components, the chain will eventually wear out with heavy use. Bike chains become ‘stretched’ over time as the pins holding them together are ground down, meaning they are no longer a perfect fit for the teeth of the chainrings or cassette sprockets.
Not only does this add to the wear on the rest of your drivetrain, it also increases the likelihood of the chain slipping off while you’re riding.
You can check the condition of your bike chain with a simple tool called a chain wear indicator.
Similarly, your chain can be damaged by an impact, debris caught in the drivetrain, or by a dodgy repair job. If one of the links is bent out of shape, the chain will need to be replaced, as it will keep slipping off the teeth and can also cause further damage to your drivetrain.
Your chain could also be the wrong length for your bike, meaning it won’t have the right amount of tension and is more likely to fall off.
If you suspect that a fault with the chain itself could be the reason it keeps falling off your bike, check out our complete guide on how and when to replace your bike chain here!
#2: Your Rear Derailleur Hanger Is Bent
Also known as ‘frame-savers’, the rear derailleur hanger is the piece of metal that connects the rear derailleur to the frame.
Derailleur hangers are intentionally designed to break. While this may sound odd, it allows them to act as a failsafe to prevent more serious (and costly) damage to your bike’s frame.
However, once the derailleur hanger is bent, the derailleur itself gets pushed out of place. This creates all kinds of headaches shifting gears and inevitably makes your bike chain more likely to fall off.
#3: Your Derailleur Limit Screws Are Wrongly Adjusted
The derailleur limit screws restrict the movement of the derailleur cage. It’s their job to keep the derailleurs in the right position over the chainring or cassette.
However, if the derailleur limit screws haven’t been set correctly, they won’t leave the right amount of space for the derailleur to move which increases the likelihood of your bike chain slipping off.
If your chain is falling off at the front, look for the derailleur limit screws on your front derailleur. The inner screw (often marked ‘L’ for low) restricts movement inwards, while the outer screw (often marked ‘H’ for high) restricts the derailleur’s movement outwards.
If the chain keeps slipping off at the inside of your smallest chainring, you might need to tweak the ‘low’ screw. Shift the chain to the smallest chainring and take a close look at the position of the derailleur cage.
There should be a very small gap of about a millimeter between the chain and the derailleur cage. If it touches the chain, the limit screw is too tight. If the gap is too wide, finely adjust the screw until it’s in just the right place.
If your chain is falling off the outside of the largest chainring, the process is the same – but you’ll need to adjust the ‘high’ screw instead.
If your chain keeps slipping off at the back, the rear derailleur limit screws might need tweaking.
A word of caution, however – there is more potential to damage other components of your bike by incorrectly adjusting the derailleur limit screws at the rear than there is at the front. If in doubt, it’s best to take your bike to a mechanic to be on the safe side!
#4: You’re ‘Cross-Chaining’
‘Cross-chaining’ is the cyclists’ term for riding with the chain either on the biggest chainring and the cassette’s biggest sprocket or on the smallest chainring and the cassette’s smallest sprocket.
In either of these gear combinations, the chain is running at a diagonal angle between the chainrings and the cassette. Not only is this inefficient due to the increase in friction, it can also make your chain more likely to slip off.
#5: Use A Chain Catcher
Chain catchers are small plastic or metal barriers that attach to your bike’s frame to physically block the chain from falling off the inside of your smallest chainring.
Some bikes have them installed as standard, but you can also buy them separately. They’re usually fairly cheap and easy to fit.
However, a chain catcher won’t help if your chain is slipping off anywhere other than the smallest chainring. It’s also worth exhausting all the other possibilities before relying on a chain catcher, as you could be masking a problem somewhere else on the drivetrain which is causing the chain to fall off!
Time To Get Riding!
Now you know how to put a bike chain back on, you’re ready to get back on the road!
If you’re still finding that your bike chain is coming off regularly, it’s worth taking your bike to a mechanic – they might still be able to find a solution that saves you replacing your entire drivetrain!