Bike chain coming off is considered normal. But a chain that starts falling frequently will not only ruin your mood but also disturb the ride. It’s a major safety concern that must be fixed at its earliest.
There are several reasons for bike chains to start coming off. Most commonly the screws are loose or the drive train alignment gets disturbed due to riding on rocky or bumpy terrain.
If you try to ignore the chain coming off this may cost a new chain. Even the drivetrain is also due to the chain slipping during a fast-speed ride. It may stuck in between may get you in any accidents.
To avoid any mismanagements you must keep an eye on your chain health and tighten any bolts or screws if loose.
Also, if you find your chain being loose or getting off more frequently than usual. Then figure out what is causing this problem. So that you can get it back on track. In case it needs replacement you can get one as soon as possible.
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Here we have jotted down the main mechanical problems that lead to a falling chain and how you can easily fix it by yourself.
7 Reasons Why The Bike Chain Coming Off
Now let us dive deep into the mechanics of your bike to find the root cause of this malfunctioning chain that is slipping down, making you annoyed and frustrated. Well there might several reasons that can make the chain slip off, some of the major ones among them are:
1. Chain Got Stretched
Due to prolonged use, the chain gets stretched or worn out with time. You can easily recognize the chain being stretched if the chain is falling from the front chainrings when you pedal fast and hard.
A special tool called Ruler is used to check the health of the chain. If it’s stretched then you may need to replace it to stop it from falling. Recommended replacement of the bike chains is 1000 to 2500 miles for smooth operations.
2. Drivetrain Parts Not Compatible
Maybe the problem isn’t with the chain itself but it is not for your bike. Yes, you heard it right! Chains are also designed according to the drivetrain components of the bike.
If bike chains are not compatible with the other hardware, they won’t fit properly and will keep coming off. Always read the manufacturer manual before replacing a new chain so that you get the one that works in harmony with your drivetrain.
3. Problem With The Derailleurs Adjustment
If you find your chain slipping off still then you must check your gear shifting system. Both the rear and front derailleur have two limit screws to ensure that the chain doesn’t fall from either side of the cassette.
If these screws are not properly adjusted then the chain may keep coming off and can get stuck between the frame and cassette. So have a look at both the front and rear derailleur to adjust the screws properly.
4. Derailleur Alignment
For extra protection of the derailleur frame, a metal hanger is attached on top of it to prevent any damage from bumps and shocks. Derailleur needs to be in perfect alignment with the cogs of the cassette for smooth shifting of gears.
If this hanger somehow gets bent it may affect the alignment of the derailleur causing the chain to not shift properly or keep slipping off.
5. Damaged Teeth
With rough and prolonged use of chain the drivetrain components may get damaged, this includes the teeth on the cassette and chainrings to worn out.
Now even after you replace the chain the chain wouldn’t fit the teeth of the cogs of the cassette properly and will keep coming off during the ride.
6. Shifters Quality
Another reason for the chain to slip is the quality of shifting system components. If the cable that shifts the derailleur has incorrect tension or causes the derailleur to shift unnecessary it will also affect the fitting of the chain and make it slip too.
7. Due To Hard-Hitting On Bumps
Due to the rough or bumpy terrain or hitting a hard rock the chain may come off due to the jerk. This is a common factor in mountain bikes or if you are using the bike for racing or sports.
So to avoid the chain from coming off during the rough route it is better to upgrade your drivetrain to a more reliable and heavy-duty one so that it performs well enough under high tension and won’t let the chain slip.
Look Carefully At Where The Chain Is Slipping!
So before starting to fix the chain slipping problem you must look for where the chain is dropping from. Either it’s the front wheel or the rear one, it is dropping inwards or outwards.
This way you can pinpoint the problem area and can fix it quickly. Here is how you can fix the chain from slipping off in different areas:
How to prevent it from slipping at the front
If you see that the chain is slipping off on the front wheel, then you must look for the adjustment of limit screws of the front derailleur that either they are tightened properly or not.
Adjust The Front Screws
The front derailleur has two limit screws one higher marked H and one lower marked L. the higher screw limits the chain from falling or moving outwards of the cage while the lower screw limits the chain movement inwards of the cage
First, you have to look where the chain is slipping
For inwards falling shift the chain to the highest gear with the smallest chainring
The inner plate of the derailleur must be in contact with the chain at a distance of 2mm
If the distance is more than that then you must move the lower screw in a clockwise position to fix the inner plate back at an optimum distance to the chain
If the chain is falling outwards then set the chain at largest chainring and smallest gear setting
The outside plate of the front derailleur cage must barely contact with the chain
Check if the gap is more than 2mm screw it in a clockwise position to fix the cage plate inwards.
Pedal The Chain Back
Another quick method to fix the chain that has fallen off during the ride is to pedal back off fast while riding to get the chain back on and you can ride further a bit to reach a safe place to fix the chain properly.
Also, you can attach a chain catcher with the casket so that it will prevent the chain from falling off as it acts as an arm that catches the chain if it is moving towards the inner cage.
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How To Stop Bike Chain Falling Off On The Rear Wheel
If you find that your chain is slipping from the rear wheel, try to adjust the rear derailleur screws, here is how you can adjust the rear derailleur of your bike:
Adjust the rear limit screws
If the chain is slipping towards the inside of the rear cassette then you must adjust the lower screw
Set the chain to the smallest chainring and highest gear
Move the screw in a clockwise direction until the rear derailleur cage that is hanging downwards comes to the middle section of the bike
Adjust until the chain can move freely in the largest gear and can’t go any further
If the chain is falling off on the outside of the rear wheel you need to fix the higher screw
Set the chainrings at the largest setting and gear on the rear wheel at the smallest
Turn the screw to make the cage adjust on the middle of the bike and adjust that it moves freely in the smallest gear
Check that your rear wheel is fitted properly. Sometimes the problem is caused by the wiggling of the wheel instead of the derailleur.
What If The Steps Above Don’t Work?
If these above steps don’t resolve your chain dropping problem then you must apply the following steps to fix it
Adjust The Derailleur Pulley
Sometimes the derailleur pulley gets bent or moves from the position. Due to its misalignments, the chain may start dropping. To adjust the pulley you must change the gears on the standing bike.
Then see that pulley and chain are aligned with each other. If not, then you need to fix the pulley to the correct position, or if it’s bent then fix it.
Check The Chainrings And Chain Line
Check whether the chain line or chainrings are bent or worn out. You need to fix them so the chain fits properly and doesn’t fall off during the ride.
Position The Crankset And Bottom Bracket Properly
You must also look for the derailleur cage and the drive train to be aligned properly with each other. If the cage has moved then you need to clamp it back on the position.
With a band clamp and barrel adjuster, you have to clamp the chain and then apply cable tension with a barrel adjuster in both clockwise and anticlockwise directions to check the system slack. Then fix the cage as same as the screws were adjusted above.
Now reset the cable tension and move the shifter to check that it is operating smoothly or not.
Other Possible Problems:
If these aren’t the problem with your chain then some other problems that might exist are
1. Chain Angle
The chain angle you are running the bike is not correct that is causing the chain to get stretched and drop.
2. Problems With The Jockey Wheel
Maybe the jockey wheel of your bike is worn out or not fixed properly which is causing the problem. Get the jockey wheel fixed in the correct position or replace it if needed.
3. Chain Length Or Damage In The Drivetrain
Another problem may be that your drive train is either worn out or damaged that is causing the alignment issues. Or the chain length is too large or small that it falls during the gear shifting.
Hopefully, these easy steps will help you out in fixing your slipping chain back to the cage. You can look out for the damaged teeth or cogs if the derailleur and drivetrain are perfectly aligned and adjusted.
Sometimes the cage also gets bent during accidents or bumps. You can easily get it back in shape, or get the chain to tighten up easily.
If you are still unable to figure out the problem and it is still slipping off then a better and safer option is to get professional help. This will save you from all the hassles and will fix the issue more quickly and efficiently.