How to Fix an Electric Bike Chain That Keeps Falling Off

You might be familiar with this already: whenever you shift gears or put some weight into your pedals, the bike chain keeps falling off. Although you can fix it by sliding the loose chain back into the front or rear chainring (wherever it “derails” from), it is only a temporary fix.

So, why does this keep happening to your ride? And how to fix an electric bike chain that keeps falling off?

Despite being an annoying thing, you can fix chains falling off and make sure it won’t happen anymore by adjusting the derailleurs and making sure that the chain’s groove falls into place every time. 

Unfortunately, not everything is as simple as a bad derailleur adjustment; there are more complicated issues underneath the surface. So, to help you understand the scope of this issue (which is relevant to both electric bikes and regulars), I’ve prepared this whole article. Bear with me as we figure out the reasons why this phenomenon: “bike chain falling” keeps happening.

How to Fix an Electric Bike Chain That Keeps Falling Off

As promised, here are some of the most common reasons why bicycle chains keep falling off, along with how you can fix it such that it won’t happen again. (At least, for a long time)

Rear Derailleur is Not Adjusted Properly

The primary reason why many bicycle chains fall off is because of bad derailleur adjustment, specifically on the rear derailleur, which is most likely to derail with improper shifting. When you shift gears to the extreme (which can be the lowest gear or the highest one), the bike chain keeps falling out of alignment with the larger or smaller chainring.

To prevent this, you need to readjust the limit screws on the rear and front derailleur. Here’s a quick guide on how you can adjust them:

1. First, keep your bike steady and hoisted up on a repair stand.
2. After that, keep pedaling and slowly shift the gears until the chain goes into the highest/lowest gear (either extreme).
3. Check the shifter indicators and see if the shifter can twist or press any further.
4. If the shifter hasn’t reached its limit, stop pedaling and put the shifter to the highest/lowest gear. (Don’t pedal, as this will derail the bike chain.)
5. Now, adjust the limit screws so that the derailleur doesn’t move out of alignment with the smaller/larger chainring. (There will be engravings near the screws with “H” and “L” indicating which one to turn.)
6. Now, let go of the derailleur slowly and start pedaling. If the derailleur is in alignment with the chainring/cassette while the shifter is indicating the correct gear, you’re all set.

Note that this method works for the front and rear derailleurs on any gear limit. For a more visual guide, check out this video for a rear derailleur and this one for a front derailleur.

Gear Shifters are Not Compatible with Your Derailleurs

Apart from falling out of alignment, another reason why your derailleurs won’t play nice with the shifters is because of incompatible or low-quality components. If your bike’s main transmission system needed some replacements, you (or whichever repair shop you took it to) might have replaced the original bike setup with other components that are not ideal.

When this happens: the derailleurs will always fall out of alignment, drive the bike chain out of the cassette and seize the drivetrain by lodging the chain into the spokes, hub motor, or the chainstay.

So to prevent this from happening, make sure you replace the drivetrain with original parts, do proper maintenance and get it installed by a professional. (Although it never hurts to invest in a chain tool and learn to do it yourself.)

Shifter Cable has Rusted or Lost Tension

Unlike belt drives, chain drives with their derailleurs and exposed shifter cables are made of metal (usually alloy steel) and constantly exposed to dust and water. So (despite being corrosion-resistant), these metal bike chains and shifter cables will eventually rust. On top of that, they will also lose their tensile strength, resulting in loose chains and wobbly shifter cables, causing the derailleurs to skip gears. (Bicycle chain keeps falling out of alignment, eventually derailing from the cassette or the smaller front chainring).

So whenever you perform periodic maintenance, don’t forget to check the shifter cables for any damages or looseness. If the cable feels a little loose, retighten the cable on the derailleur. (You might need Allen keys, a screwdriver, and a pair of pliers.)

Improper Shifting

If you shift too erratically or use gears in extreme combinations, it can put undue stress on your bike chain, creating a loose chain that keeps falling off the drivetrain.

So make sure to switch gears one by one and stick to the proper gear combinations to minimize the chain falling out of alignment.

As a rule of thumb, whenever you change gear on the right shifter, make sure not to go lower than the left shifter’s number. Also, ensure you don’t exceed that number by five gears.

For example: after shifting into the third gear on the left shifter (front derailleur), never go lower than three on the right shifter (rear derailleur), and when you have shifted onto the first gear on the left, don’t go higher than the fourth gear on the right.

Here’s a more detailed explanation of this situation.

Drivetrain Components are Coming Loose

Although it is unlikely (unless tampered with), the drivetrain bolts that keep it together can loosen up and cause the bike chain to fall out from the largest or smallest sprocket.

So, to make the process easier, where the bike chain keeps itself inside the chainrings at all times, I recommend carrying out frequent maintenance on the bicycle’s drivetrain, or at least a thorough visual inspection once a week.

The Chain is Dirty or Rusted

Whenever you have mud, dirt, or grime caked in between the links on roller chains, it can damage the cassette teeth or not fall into them at all.

The solution is simple: clean your bicycle chain regularly using a bicycle brush and chain cleaner. Clean it out and lubricate it regularly (at least once a week), and if you don’t have a dedicated brush improvise using an old toothbrush or two.

Chain is Too Long

Either the chain has deteriorated or you didn’t figure out the correct chain length for your bicycle, whatever the case may be if you see that the chain is lagging at any gear combination you will face (or have already faced) a situation where the chain pops off from the drivetrain.

So try some of the common ways to diagnose this issue such as using a chain wear indicator tool, adjusting the chainstays, or checking for defects on the rear derailleur, and if the chain is just too long and not worn out, you can get it replaced for a shorter one or remove some links and get it up to the correct length. (As long as you have the proper tools and are gentle with the chain.)

The Cassette Teeth have Worn Out

Worn-out chains can be the least of your problems when you’ve got a chainring with no teeth. The chain will just slide off the largest sprocket it comes into contact with like water off a duck’s back.

Removing a crankset (including the front chainring and rear chainring) is not so easy as it requires certain special tools, but with some time and effort, you will be able to do it yourself. Although if you can’t, it’s best to leave it to a professional.

Damage to the Bicycle Frame and Drivetrain

Also, if the frame near your rear wheel/drive wheel is deformed, it can cause issues where the bicycle chain would fall out from the sprockets and into the chainstay. So whenever you get into a crash or have your friend return your bike (after he borrowed it), make sure to assess the damage and check for any dents or defects in the chainstays, bottom bracket, seat stays, and even the E-bike’s drivetrain.

How to Replace/Reinstall a Bicycle Chain

Whenever the chain pops out or you need to replace your worn-out chain, follow these steps to put it back in securely:

• Keep the bike steady (either on a repair stand or leaning on yourself).
• Create some slack in the bike chain by moving the rear derailleur towards the front of the bike.
• Now pop the chain back into the chainrings and make sure it has caught on enough teeth
• Let go of the derailleur slowly
• Do a first backward rotation using the pedals so, the chain links get positioned correctly
• After that, lift the rear tire and do a couple of front rotations.
• That’s it! You’re good to go and derail your chain, again.

Common Question: Do I Need to Carry a Chain Tool with Me?

I highly recommend keeping a chain tool in your bicycle repair kit; you never know when you get a bent link and need to add links. Therefore, a chain tool is just as important as a puncture kit.

Chain tools are usually very compact and don’t take up as much space. If your chain has a master link, you might only need to carry a master link plier with an extra chain, but if you have a regular chain, you might need to use the chain splitter tool.

I recommend this kit for beginners, it’s better suited for master links, but the chain splitter tool is very useful.

Conclusion

Whenever a bike chain won’t stay inside the sprockets, it’s almost always a fault in the drivetrain, specifically the rear derailleur. However, if you’ve adjusted the derailleurs and made sure that the components work with each other seamlessly, it might be time to consider wear and tear on the other components.