Reasons why your chain may be falling off your bicycle

If you've ever wondered why your chain always seems to fall off your bicycle, here are some reasons why. This is a compilation from experience and lots of diagnosis.

1. You may be jumping your bicycle too high and landing too hard.

2. Your chain length is too long. You need to shorten, probably by removing one link at a time. Measure by shifting into the largest cog in the back (lowest gear) and shifting to the largest chainring (in the front). Although not a good practice, shifting into these gears will indicate your chain length limit. If you can't do the aforementioned, then it's probably not the chain length that's the problem.

3. If your chain skips and then falls off, you probably need a totally new drivetrain.

4. Your rear derailleur might not have enough tension.

5. You powered on a larger gear than you should, thus breaking a link.

6. Your derailleur has disappeared. (I've seen this happen.)

7. Your chain has stretched - in which case, replace it.

On older bikes, this is much more common.

As a bike ages, the tension in the cables that control your brakes and derailleurs slowly slackens. This means that the derailleur, which is usually sprung toward your outermost gear, isn't held in place quite as effectively as it used to be, and so, when changing into your highest gear the chain misses and you're left without a drivetrain.

If the bike is new, and the chain is falling off the chain rings at the cranks, it is most likely that the bike was adjusted with too much tension on the front derailleur before it left the shop. This is fairly common as the cables, while new, have a small amount of elasticity which vanishes fairly quickly with use and exposure to the elements.

On a well maintained bike, the chain should never just fall off, under any circumstances. That includes a full sprint from a standing start in top gear. If it does, take it to a bike mechanic.