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My chain has a tendency to frequently jump off the front chainring. I have a 1x9 so it's not a front derailleur issue. It generally happens when I hit something like the lip of a driveway or sidewalk at a crosswalk, which sucks when it pops off in the middle of crossing a busy highway in town. Could my chain be a bit too loose?

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Is your front chainring on the outside or inside of the spider? Is it a converted 1x9 or did you purchase it as a 1x9?

It's most likely happening when you hit large bumps or holes in the road. It's possible that your chain is too long if you converted it from a 2x9 and didn't reduce the number of links in the chain.

If you converted it, it's also possible that the chainring is just too far away from your center line for a proper chainline when you're on your largest cog. If possible, move your chainring to the inner side of the spider. If you have a single ring crank, you may need to get a shorter BB/spindle.

Another cheaper and easier solution is to get a chain watcher. There are several types and brands such as N-stop, K-edge, Paul Components. This will sit on the inside and/or over the top of your chain on the front chainring which will help prevent the chain from jumping off the front ring. They are used widely in the cyclocross world to prevent this.

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    I've also had issues running a 1x9 setup on some full suspension frames. Whenever the frame linkages compress, the momentary slack in the chain would invariably let the chain fall off. There are chain tensioners and chain keepers specifically designed for heavy off road use.
    – WTHarper
    Aug 22, 2012 at 15:46
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    Another option would be to mount an inner and outer bash guard---essentially they are smooth chain rings which protect the profile of your chain ring (the Salsa Crossing Guard is specifically for chain retention). These can be used in conjunction with a chain keeper (like the Paul Comp).
    – WTHarper
    Aug 22, 2012 at 15:49
  • Tha Riddla: It was originally built as a 1x9, it wasn't converted. I'm not sure if it's on the inside or outside of the spider, I'd assume inside. It does have a bashguard on it in place of the outer ring.
    – Ryan Arneson
    Aug 22, 2012 at 16:30
  • WTHarper: It definitely feels like slack when hitting the bumps could throw it off. Even if I stop pedaling abruptly the chan will slap the frame. I'll look into a chain watcher.
    – Ryan Arneson
    Aug 22, 2012 at 16:32
  • While I still feel a chain watcher is the way to go, I can't help but think something is still a bit off in my setup. I've thrown the chain off 3 times in the last two days, and from tiny little bumps, like the lip of a driveway. Should I try to remove a link in the chain? What are the drawbacks if it ends up being too short? I assume I'll have issues shifting.
    – Ryan Arneson
    Sep 25, 2012 at 15:40

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