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  1. #1
    Senior Member
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    Jan 2007
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    Chain length and derailleur mount break

    Folks, recently the derailleur mount on the bike has snapped while climbing a moderately steep hill. The derailleur mount if actually screwed to the frame so it can be replaced easily. Apart from the mount, the chain broke and the derailleur cage was slightly bent. All that went going uphill.

    In retrospect I'm sure I'd have some leeway if I'd climb the same hill with the Cannondale badboy in the same very low gear. But with the recumbent I was in direct drive so to speak and since it seems I have some leg power I was just pushing the cranks to get up there when everything snapped.

    So my question is, I think it can be possible to be in such a position if the chain is too short. I might have cut the chain to short after adjusting the boom. So when climbing that hill the chain would have exerced too much pressure on the mount. Can this be possible ?

    Everyone knows I have an AB HiRacer. I must say that AB did not hesitate one minute in sending me new derailleur mounts. Very good service. To their record they've never seen that kind of incident.

    So I think so far that it is my fault by cutting the chain too short. Basically on the recumbent I should have the same leeway (of course this depends on the cogs and chainrings) when climbing uphill than on a regular bike. I should be spinning and grinning going uphill and not be in 'direct drive' of the rear wheel where it feels that every turn of the cranks makes the wheel turn once as in a very steep mountain bike type bump.

    Cheers.

  2. #2
    Senior Member
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    Sep 2006
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    Aurora, CO
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    2005 Performer Toscana, 2000 Kona Hoo-Ha, RANS Rocket
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    What chainring were you using? Did you change the boom length recently? When installing a chain, normal procedure is to put the chain on the biggest ring and biggest cog, and adjust length so that the two ends overlap by about an inch.

  3. #3
    Cycling Anarchist Trsnrtr's Avatar
    Join Date
    Jun 2002
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    One of the young mechanics at my LBS "optimized" my chain for me one time and I inadvertently shifted big/big on a hill and bent the front idler mount horribly. He had removed two links to try and help me with what he perceived as "too much chain flop."

    I do all of my own work and this was a rare case of taking a bike in for a free 500 mile checkup. All I really wanted was for someone else to clean my chain!

    Back to the original question, yes, a too short chain can cause some serious damage if you aren't careful.
    Dennis T

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