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Kids Bike Dropping Chain

Postby cep32 on Thu 19/Oct/17 9:01am

My son rides a Specialized Riprock 20" and is always dropping the chain off the front. The bike came with a top chain guide and that seems to keep the chain on when he is pedalling forward. The problem comes when he back pedals half a rotation to drop his outer foot on turns. Any time he rolls the bike backwards it does the same. It looks like it is dropping off the bottom of the chainring.

The chainline isn't great so I'm putting in a slightly narrower bottom bracket.

Is there anything else worth trying other than a full-on downhill chain guide?

Member for: 7 years 7 months

Re: Kids Bike Dropping Chain

Postby matnz on Thu 19/Oct/17 11:29am

Problem I had once with my boys bike. I ended up upgrading derailleur to an old XT I had lying around, and putting on a decent quality (but half worn) chain and fixed it - more accurately improved it enough it was no longer a problem when riding. Sorting the chain line cannot hurt.

From what I have read KMC chains are better than Shimano when it comes to back pedal dropping, and the problem improves as the chain wears a bit. The problem seems to be around the chain being too stiff side to side, and back pedaling nothing holds the chain on the chainring.

Also from what I have read, if you want to fix it reliably without faffing around, a full on Chain guide is the the best way.
Member for: 3 years 5 months

Re: Kids Bike Dropping Chain

Postby wachtourak on Thu 19/Oct/17 5:58pm

Narrower BB will hopefully fix it. I remember when selling similar kids bikes a few years ago the chainlines were always super mainging, but the manufacturer refused to acknowledge the problem. Shorter spindle BB fixed it.

We had some city/urban bikes with a single ring that had the same issue, again shorter BB spindle worked.
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Member for: 15 years 10 months

Re: Kids Bike Dropping Chain

Postby cep32 on Fri 20/Oct/17 10:19am

Awesome. Thanks guys. A workmate has just donated a full 10 speed Deore (with clutch derailleur) so I'll put that on this weekend and see how it goes. A narrower bb will be installed next week if needed as well.
Member for: 7 years 7 months

Re: Kids Bike Dropping Chain

Postby cep32 on Tue 24/Oct/17 9:59am

Just an update for anyone who searches the topic in the future. Replacement of the stock bottom bracket with a narrower 110mm wide one improves the chainline enough that the chain stays on the front ring when back pedalling.

Thanks for the advice all.
Member for: 7 years 7 months

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