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Discussion Starter · #1 ·
I bought my 7 yr old son a used Specialized Boy's Hotrock A1 FS 24 which has been a great bike with one exception.......the chain seems to fall off every once in a while. I took it into the LBS for a complete tuneup when it was purchased and when I put it up on a rack, it shifts just fine and the derailleur stops seem okay. Once in a while though, the chain just seems to jump off the chain ring and get stuck between it and the frame. I do notice when I ride behind him that the chain does seem to whip around quite a bit. I am thinking maybe a new chain might do the trick but am open to suggestion from anyone out there who knows what they are doing.

Thanks,

Dave
 

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Vaginatarian
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djphaneuf said:
I bought my 7 yr old son a used Specialized Boy's Hotrock A1 FS 24 which has been a great bike with one exception.......the chain seems to fall off every once in a while. I took it into the LBS for a complete tuneup when it was purchased and when I put it up on a rack, it shifts just fine and the derailleur stops seem okay. Once in a while though, the chain just seems to jump off the chain ring and get stuck between it and the frame. I do notice when I ride behind him that the chain does seem to whip around quite a bit. I am thinking maybe a new chain might do the trick but am open to suggestion from anyone out there who knows what they are doing.

Thanks,

Dave
check the front chainrings (gears) for bent or broken teeth.
check the chain for tight links
make sure he isnt cross gearing. (little front to large rear or vice versa)
could also be chainsuck, (chain doesnt release from front gear, wraps around) usually from worn out chainrings
since the bike was used I would check out the front chainrings first, if you dont change the chain enough the gears wear to fit the worn out chain, make sure the teeth arent hooked or nubs. the chain should be 1 foot from pin to pin if its off more that 1/8" you need a new one, and prob. rings too.
 

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Discussion Starter · #3 ·
I think you got it with your first suggestion, unless some of the teeth are designed to be flat on top instead of pointed. I never really looked that closely at the gear teeth. Next problem will be finding a replacement. Strange, because they still make the same bike with a Truvativ ISO-Flow crank set but I can not find any on line. Also would be a bit wary about buying chain rings. Would rather fix myself, but Will try to take it into LBS and see if they will help without robbing me blind.

Thanks for the help!


Dave
 

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Discussion Starter · #4 ·
Update is that I replace the small chain ring up front and got a new chain. Thought this would do it, but still had his chain fall off on the ride tonight. It still looks like the chain is whipping around a lot while he is riding and I am at a loss again.
 

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Mechanically, it's more likely to be the position of the front derailleur that is allowing the chain to leap off. However, there's also the possibility that he's just riding certain terrain in an inappropriate gear (low gears at high speed, for example). Going over jumps and bumps in a low gear is likely to end up with the chain coming off because the rear derailleur is not able to apply sufficient tension to keep it on.
 

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My wife was having a similar problem with a perfectly tuned bike. Her issue was what she was in the granny gear up front and down to 7-8 in the rear, there was just too much chain for the teeth. once I showed her how to toggle between the granny and the middle ring, this has eliminated the issue. She is a newbie rider.

What gears are you in when this is happening?
 
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