A chain is an essential part of a bike. It transfers power from the pedals to the drive-wheel, propelling you forward. When you shift, the front gear derailleur and rear derailleur move the chain, and guide them to the gear you’ve chosen. If there’s anything wrong with the drivetrain, the chain can fall off, rendering your bike useless. Check out six common reasons this is happening and how to fix it.

1. The chain is too long.

When you replace the chain, make sure the new one is lined up perfectly to the old one, and remove or add links as needed. You’ll need a chain splitter to do it correctly. If you’ve already discarded the old chain, adjust the new one until you don’t have so much slack.

2. The chain or another component is worn out.

Sometimes a part isn’t broken or bent, it’s just worn out and needs to be replaced. It could be the teeth on the crankset or chainring, one or both of the derailleurs, the pulley spring, or something else. Check everything and replace what’s past its time.

3. Something is loose in the drivetrain.

Move through all drivetrain components to see if anything is loose. Don’t pull on anything too hard, otherwise it could bend or break. Just wiggle them to see if they rattle or move slightly. If they do, they need to be tightened, but not too much. Then test if you can run through the gears without the chain falling off.

4. The front derailleur is not properly adjusted.

Turn the bike upside down, spin the pedals, and shift through the gears while watching the front derailleur. You can tell if it’s off center to the gear it should be in. Adjust it so it’s exactly center over each gear.

5. The rear derailleur is not properly adjusted.

This is more common than the front derailleur being inaccurate. Follow the same steps listed above while checking the rear derailleur and re-center it as needed.

6. You’re pushing the shifter too far.

You might be pushing it past the last gear. Then the derailleur extends itself too far and the chain falls off. Make sure you’re only shifting to the last gear, no further. Many modern shifters do not allow you to push the derailleur past its limit. If that is the case, then this would not apply.

Bike Chain on a Workbench

If you need more help with your bike chain, visit us at Airpark Bike Co in Scottsdale, AZ. We’re here for all of your bike service needs, and advice for quick and easy repairs. Stop in today for a quick fix so you can get back to what you do best – shredding the trails!