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Chain slipping under load, especially in small ring

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Chain slipping under load, especially in small ring

Old 07-07-13, 03:33 AM
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frantik
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Chain slipping under load, especially in small ring

I've got a tandem that is slipping under heavy load. Chain is brand new, and this has happened on two sets of chain rings, so i'm guessing possibly the cassette is worn. I plan on replacing the cassette and hope that will solve the problem, but I noticed something which made me wonder, specifically: it seems there is a lot more slipping when the chain is on the smaller ring.

There was originally a triple crank on there, but i replaced it with a road crank which doesn't extend nearly as far out from the BB. Could the angle of the chain be affecting the slippage? And should this go away with a cassette that isn't worn out, or are there other potential issues I'm facing?

thanks
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Old 07-07-13, 04:01 AM
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Most of the time it's the cassette when the chain's jumping. It'll show up sooner on a tandem because of the extra load. You should generally replace the cassette when you replace the chain, unless you've been rotating two or more chains on the cassette.

I'd say chainline being a factor is a credible theory...

Why did you ditch the triple? They're usually a good idea on a tandem. Did you change the BB as well?

Last edited by Kimmo; 07-07-13 at 04:06 AM.
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Old 07-07-13, 04:21 AM
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Originally Posted by Kimmo View Post
Why did you ditch the triple? They're usually a good idea on a tandem. Did you change the BB as well?
the triple was a low end riveted steel POS so I swapped it with a much nicer road crank I had on hand. Where I live it's flat so a triple is overkill anyways.. since the small ring was slipping more we rode in only the 52t ring the whole time and didnt have any problem with the gearing, except for poor gear selection in our cruising range

I didn't change the BB...
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Old 07-07-13, 06:22 AM
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AFAIK most triples use longer BBs so that could be part of the issue.

Poor chainline on its own won't cause skipping on a derailer chain though.
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Old 07-07-13, 08:40 AM
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i took a look and the small ring actually seems like it offers a more straight chainline than the large ring.

I swapped on a different cassette, going to take it for a test ride..
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Old 07-07-13, 08:57 AM
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Probably the cassette and you're probably slipping more when in the smaller front chainring simply because you have more mechanical advantage which loads the drivetrain more. And you ARE slipping under load - right?
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Old 07-07-13, 09:36 AM
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yes it was only under load. I swapped the cassette and the problem went away. I guess the cassette i had is no good. I was worried there was more to it but luckily not

now i just need to figure out how to keep the timing chain on. It was fine for the first 15 miles but now it comes off on bumps and sometimes just randomly. I guess the chain stretched a tiny bit and now i have to adjust the idler gear. i hope it doesnt need to be adjusted every 15 miles though

edit: for now i'm going to try a ghost ring + idler.. it's not pretty but it's a lot easier to adjust the ghost ring than the idler

Last edited by frantik; 07-07-13 at 10:36 AM.
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