# my bicycle chain keeps derailing when i hit a bump



## DominicTabuzo (Oct 2, 2012)

whats seems to be causing this problem?

here's a photo of my gear setup


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## Betarad (Oct 24, 2009)

Looks like you could shorten your chain by a link. And make sure derailleur spring tension is maxed.


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## DominicTabuzo (Oct 2, 2012)

Betarad said:


> Looks like you could shorten your chain by a link. And make sure derailleur spring tension is maxed.


derailleur spring tension? how do i adjust that?


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## Harold (Dec 23, 2003)

Not sure what betarad is talking about regarding derailleur spring tension (are you talking about the b screw?), but most 1x9 systems benefit heavily from a chain guide of some kind on that chainring. 

But definitely a loose chain from being too long or being in a smaller cog will allow that chain to jump off easier. It almost looks like you have a medium or short cage derailleur on already, which can help.


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## DominicTabuzo (Oct 2, 2012)

NateHawk said:


> Not sure what betarad is talking about regarding derailleur spring tension (are you talking about the b screw?), but most 1x9 systems benefit heavily from a chain guide of some kind on that chainring.
> 
> But definitely a loose chain from being too long or being in a smaller cog will allow that chain to jump off easier. It almost looks like you have a medium or short cage derailleur on already, which can help.


oh cool ok tnx man


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## AndrwSwitch (Nov 8, 2007)

The chain on a multispeed bike rattles around a lot. On a bike with a front derailleur, the front derailleur prevents the chain from falling off. On a singlespeed, the chain doesn't have enough free length to fall off. You have a multispeed bike with no front derailleur. So you need something else.


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## DominicTabuzo (Oct 2, 2012)

AndrwSwitch said:


> The chain on a multispeed bike rattles around a lot. On a bike with a front derailleur, the front derailleur prevents the chain from falling off. On a singlespeed, the chain doesn't have enough free length to fall off. You have a multispeed bike with no front derailleur. So you need something else.


oh thats what i need a front derailleur


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## Harold (Dec 23, 2003)

DominicTabuzo said:


> oh thats what i need a front derailleur


you can use a front derailleur as a chain guide, too, but there are specific products you can buy (many different types) that can do the job, too.


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## ThundaCrymz (Oct 22, 2012)

Well you don't really need a front derailleur if you don't have to shift gears in the front, but i guess it could be good as a guide. I also think you should measure your chain and make sure it's not too long, you should shift the rear to the smallest cog and see if you have a alot of slack in the chain as well. 

Alternatively, to check your chain length, you could get a chain tool and detach your chain, run it out of the rear derailleur, then with your detached chain, wrap it around the largest cog in the back and the front chainring, and pull the two ends towards each other, if the chain overlaps the two ends being pulled towards each other then it's too long. you'll want it short enough where only 2 sets of links will overlap the ends.


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## Betarad (Oct 24, 2009)

DominicTabuzo said:


> derailleur spring tension? how do i adjust that?


Yeah, the B screw is what I meant. A single screw generally located somewhere at the back of the rear D mount pivot. It won't increase chain tension in a huge way, but if you're dropping the chain regularly, maxing the B screw tension can only help.

I agree with Andrw that without a front D the chain is more likely to drop off the chainring. You may ultimately need to install a chain tensioning device. But, judging by the relaxed position of your derailleur in the pic, I still think you can maximize the chain tension on your current setup and help the situation by shortening the chain by a link.


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## DominicTabuzo (Oct 2, 2012)

ThundaCrymz said:


> Well you don't really need a front derailleur if you don't have to shift gears in the front, but i guess it could be good as a guide. I also think you should measure your chain and make sure it's not too long, you should shift the rear to the smallest cog and see if you have a alot of slack in the chain as well.
> 
> Alternatively, to check your chain length, you could get a chain tool and detach your chain, run it out of the rear derailleur, then with your detached chain, wrap it around the largest cog in the back and the front chainring, and pull the two ends towards each other, if the chain overlaps the two ends being pulled towards each other then it's too long. you'll want it short enough where only 2 sets of links will overlap the ends.


ya ya whatever, ya iknow thats why im gona screew this back


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## AndrwSwitch (Nov 8, 2007)

Is that a multispeed chainring you're using right now? If so, that makes things even worse. Modern chainrings are designed to shift well, and they do. If there's nothing to control that motion, the chain will fall off from time to time, facilitated by the features that help make it easier to shift.

If you wanted to do 1x, there are plenty of products out there purpose-built to help you do it. That's what I was thinking of when I said you need something else, if you don't use a front derailleur. Paul Components and MRP make some. Using a bash guard and an inner jump stop is another method. My only single-ring bike is a track bike, so I have no experience with any of these products myself. But it's discussed a lot over on the drivetrain forum.


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## 50calray (Oct 25, 2010)

DominicTabuzo said:


> whats seems to be causing this problem?
> 
> here's a photo of my gear setup


Hum...I would try a Bionicon Chainguide. If that doesn't work, you may need something like a chainguide that attaches to your chain ring like an E13.

E.thirteen E13 SRS+ Plus IS-05 BB Bike Bicycle Chain Guide 32t-36t - Black on eBay!


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## jjaguar (Oct 6, 2011)

Can you post a pic with the chain on the big cog? Then we'll be able to judge chain length better.


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## Gasp4Air (Jun 5, 2009)

I'm guessing your chain is more than 1 link too long. Here's how to check: Distance around biggest gears + 2 links

1 Remove the chain. 
2 Bypassing the rear derailleur, wrap the chain around the front ring and the biggest cog.
3 Pull the chain ends together, note where they meet.
4 Add two links overlap, remove the rest.

As mentioned, if your cage is long, a medium would help, as would a chain guide.


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## DominicTabuzo (Oct 2, 2012)

jjaguar said:


> Can you post a pic with the chain on the big cog? Then we'll be able to judge chain length better.


:idea:


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## shibiwan (Sep 2, 2012)

That chain looks a little long for that setup. Try removing a pair of links and see how far the the derailleur cage moves.


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## Harold (Dec 23, 2003)

a tourney derailleur. hmmm...not sure if that's a longer or shorter cage...those have big jockey pulleys that throw off the perspective.

either way, a tourney derailleur is not going to have the same spring tension as a more expensive model. that might be one of the problems. your chain is just going to bounce more. ESPECIALLY compared to a more expensive derailleur with a shorter cage.

MAYBE you can shorten the chain a little...but you still didn't post a pic of the chain on the biggest cog so it's difficult to tell how stretched out the derailleur would be taking up the minimum amount of slack necessary.

regardless of that, though, a chain guide of sorts would help you, too. most 1x9 setups benefit from one.


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## AndrwSwitch (Nov 8, 2007)

Article I like on chain sizing.
Park Tool Co. » ParkTool Blog » Chain Length Sizing

I think you'll still need some retention up at the crank, though.


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