Why Your E-Bike Chain Keeps Falling Off

In plain English

A chain that falls off, especially under motor power, can jam and damage the derailleur or frame. Where it falls tells you the cause: off the smallest or largest rear cog points to gear limits, off the front chainring points to chain line or a missing chain guide.

Watch how it's done

Video by Park Tool. It may show a regular bike: on an e-bike, switch off and remove the battery first, and unplug the motor cable before taking off a hub-motor wheel.

Work from the top. Steps go from free and easy to shop jobs. Switch the bike off before touching any connector. Tick each step as you go. Your progress is saved on this device.

1. 1Note where it falls offFree Off the big or small rear cog, or off the front chainring? Under power, or over bumps?
2. 2Check for a stiff linkFree Turn the pedals backward and watch the chain. A stiff link can throw the chain off. Flex it loose and lube it.
3. 3Check chain wearEasy A worn chain comes off more easily. See our chain wear guide.
4. 4Fine-tune the gearsEasy Try a quarter turn of the barrel adjuster. If it falls off past the biggest or smallest cog, the derailleur's limit screws need setting, which a shop can do quickly.
5. 5Have the gears and chain checkedShop job A shop can straighten a bent derailleur hanger, set the gear limits and replace worn chains and cassettes.

Parts you might need

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Only buy a part if the free steps didn't fix it. Always match the voltage and connector type to your bike.

• Bike chain

  Match the number of gears on your bike (for example 8-speed). E-bike rated chains last longer.

  Link coming soon

• Chain wear checker

  A small gauge that tells you when a chain is worn out.

  Link coming soon

• Chain lube

  Keeps the chain quiet and stops wear. Use bike chain lube, not household oil.

  Link coming soon