As a cyclist, I like to share common cycling problems to help riders head off problems before they get serious. And having the bike chain fall off while pedaling backwards is one of those frustrations all cyclists have dealt with.
Most people assume a chain falls off because it is too loose. While this is a common reason, there are additional factors to consider. A lack of tension, dirty components, bent or broken parts, and poor alignment can all cause the chain to fall off.
As a cyclist, I understand how important it is to take proper care of your bike. I put this guide together to help you identify the lesser known causes of fallen chains to help you do so.
If any of the chain mechanism components are in a less than optimal state, any small jump or bump can knock the chain loose. It can also slip right off when pedaling backwards.
Not realizing the chain is off can cause it to get jammed between the frame and crankset which causes serious damage to the bike.
This guide will help you find out what is causing your chain to fall off so you can get right to the problem and right back to riding
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Table of Contents
Loose Chain
A loose chain is the first thing people look for if the chain falls off. It is a common occurrence, but it is not the only reason. A loose chain is often caused by inadequate tension.
A loose chain can get caught in the spokes or damage the frame. You can still ride if the chain is a little loose, but if it is falling off then chances are you need to get it tightened right away.
The bike chain is a crucial part of the bicycle. As you pedal it transfers power to the wheels so you can move. A loose chain means less power transferred. A loose chain on multi-gear bikes can also be a hazard if your foot were to get caught in it.
If, like me, you cycle regularly, you will have had your run-ins with loose chains. They are easy enough to fix so long as you catch them before any damage occurs.
- Flip your bike upside down and locate the derailleur screw.
- To increase tension on the chain and reduce looseness, turn this screw clockwise.
- You also need to adjust the rear tire.
- Disconnect the brakes from the cable and lift the brake lever to get access to the rear tire.
- Slide the wheel axle toward the rear dropouts to tighten the chain.
- Make sure you do not tighten too much. You only want to adjust enough to get rid of any slack in the chain.
Bent Chainwheel
Another common reason that your chain falls off when pedaling backwards is a bent chainwheel.
The chainwheel can get bent from dropping the bike against a hard surface. Most cyclists test their chainwheels by pedaling backwards.
When you look at the distance between the chainwheel and the frame, it will change if bent. If your chain is falling off while pedaling backwards, then this could very well be the culprit.
A bend in the chainwheel means the chain is not sitting flush in place as it should. The chainwheel itself will be wobbly, and this can cause the chain to fall off when near the bent area.
I have ridden on a slightly bent chainwheel before. After dropping my bike on a ride, I was able to get it back home to repair it.
I would not recommend riding with a badly bent chainwheel as you can cause damage to the chain and frame.
A badly bent chainwheel will need to be replaced. However, if the chainwheel is only slightly bent, you may be able to straighten it. You can use a wrench to gently straighten it back into shape.
There are also specialized straightener tools you can get from a bicycle shop. Pay attention to the material of your chainwheel as aluminum is easier to straighten than steel.
Chainwheel Put On Incorrectly
In the same way that a bent chainwheel can cause the chain to fall off, a chainwheel that has not been put on correctly can to. If the chainwheel is not correctly attached, it will wobble.
The chain will also wobble as it works its way around the wheel which can cause it to come off. The chain needs to be securely attached for the bike to work.
If the chainwheel is moving and not secure, the chain will be loosened from its position. This can cause the chain to fall off when pedaling backwards or forwards, and this can be dangerous.
It can also seriously damage the bicycle frame, chainwheel, and chain. In addition to the chain falling off when cycling backwards, you may also hear a rattling sound if the chainwheel is not properly attached.
New bicycles rarely have a chainwheel put on incorrectly, but it can happen. In my experience, the most common reason for a chainwheel to be loose is when it was replaced.
Whether you are replacing a damaged or bent chainwheel or you have a bicycle shop do it, it is important to make sure it is properly attached. Perform a few tests with it to make sure it is not wobbling, and the chain is not loose.
Bad Alignment
If you are noticing noisy shifts when you rise, you could be dealing with poor alignment. Bad alignment also causes the chains to fall off when pedaling backwards.
In most cases of poor alignment, the problem is the derailleur.
The derailleur is what keeps your chain from going into the spokes or frame and prevents it from falling off the chainwheel.
Bad alignment of the derailleur can cause all of these and some serious damage during a ride.
Your bicycle will have a derailleur on both front and back wheels, so you will need to check both if you have a chain fall off.
Bad alignment will continue to cause the chain to fall off, so I would advise getting it fixed right away.
Riding with wheels and chains out of alignment can leave you with a chain in your spokes. I have had this happen and it is an expensive fix. Better to stay off the bike until it is re-aligned.
Bent Teeth On Cassette
Dropping your bike can lead to a bent chainwheel as mentioned earlier. It can also lead to bent teeth on the cassette. Bent teeth interfere with the chain’s ability to rotate smoothly.
In some cases, bent teeth will cause the chain to get stuck and in other cases it cannot support the chain, so it falls off. Severely bent teeth on a cassette may not even grip to the chain at all.
The grooves in the bike chain need to grab the teeth on the cassette in order to turn the wheels.
When bent, the teeth are a different shape and may not fit properly in the grooves as the chain passes. If it cannot grip, the chain loosens and falls off.
You can check for a bent tooth by inspection or by the same method you used for checking a bent chainwheel.
Having previously attempted to fix bent teeth on a cassette myself, I would advise to take it to a professional. Or if badly bent, simply replace the chainwheel.
Using a pair of pliers, I tried to straighten a few bent teeth, but ended up distorting the cog, which messed up the interaction between the chain and the next gear.
You don’t want to ride with bent teeth, so as soon as you notice them, get them replaced.
Stiff Link In Chain
Older bikes and those ridden frequently will experience wear and tear on the chains. A lot of wear can cause stiffness in the chain links. This can also happen if a bike sits unused for a long period of time.
Stiff links in a chain can cause it to fall off the chainwheel when pedaling backwards because they are not moving as smoothly as they should be.
The chain mechanisms on a bike need to run like a well-oiled machine. The movement of the chain needs to be smooth and any stiff links can disrupt this.
When you watch the chain on a bike as it rotates and changes gears, it will look almost fluid. A stiff link gets stuck or just pops loose from the teeth. It only takes one link to come loose for the whole chain to get slack and fall off.
You can identify the stiff link by rotating the pedals backwards. Watch the chain as it passes between and over the derailleur pulleys.
You will be able to see the stiff link as it passes by. The pulleys will suddenly move as the stiff link tightens and goes through.
Make sure you check to see if the stiff link is covered with rust, as this is a common cause.
When moisture gets stuck between the links, they can lock together with rust if not regularly lubricated. Chains with overly rusted or stiff links will need to be replaced.
For just one or two stiff links, you can replace them individually. Just be sure to get the same size links, be it 9-, 10-, or 11- speed, otherwise the chain will just pop right off again.
Dirty Freehub
The freehub is an essential component of the bike, incorporating a ratcheting mechanism to engage the bike chain. Cassettes are mounted to the splined shaft of this hub and then engage the chain.
Water and dirt can easily find its way into the internal workings of the freehub. When they get in there, they strip away any lubrication and your bike begins to sound old and rusty.
Not to mention that your chain can also fall off too. If the cassette cannot properly engage with the chain, it will slip off when pedaling backwards.
I mention the freehub because it is often forgotten when looking for the causes of a chain falling off. For bikes that see a lot of action, the freehub can get dirty so is important not to overlook.
Fixing a dirty freehub is relatively easy. It is often the first thing I check because it is such a simple fix. One always wants an easy fix over a difficult one, right?
Only in cases where there is serious damage will you need a professional to take a look at it.
To clean out the freehub simple follow the steps below.
- Remove the cassette
- Remove the axle and ball bearings and clean all of them with a rag
- Remove the freehub body using a 10mm Allen key
- Flush out the hub twice with WD-40
- Re-install the freehub (make sure to re-torque the bolt tightly)
- Reassemble the axle and bearings (these should be clean and greasy)
Helpful Tips To Know Why Bike Chain Falls Off When Pedaling Backwards
Your bike chain falls off when pedaling backwards and there are more possible reasons than you first thought. To help you better identify what is causing your problems, keep these helpful tips in mind.
- Carefully check the chain mechanisms before riding
- Look for any signs of rust
- Listen for squeaking or grinding noises
- Check for damage to the chain anytime the bike is dropped
Final Thoughts
When your brake chain falls off when pedaling backwards, there are several different causes to consider. To make sure you identify the problem, it is helpful to know what all the causes could be.
With this guide you can quickly identify what is causing your chain to fall off so you can perform the necessary repairs or replacements.
You cannot cycle without a chain, so make sure your chain stays in place so you can stay on the road.
