chain lengh and a long cage rear mech

willbevan
willbevan Posts: 1,241
edited January 2008 in Workshop
Hi guys,

Quick questiion, if you change from a short cage mech, to a long cage, will the chain need lengthening? (presuming your not changing anything else) as more chain ends up in the rear mech?

Thanks

Will
Road - BTwin Sport 2 16s
MTB - Trek Fuel 80
TT - Echelon

http://www.rossonwye.cyclists.co.uk/

Comments

  • redddraggon
    redddraggon Posts: 10,862
    willbevan wrote:
    Quick questiion, if you change from a short cage mech, to a long cage, will the chain need lengthening?

    Yes, put the gears in big front, little rear, and the jockey wheels should sit in line vertically.
    I like bikes...

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  • willbevan
    willbevan Posts: 1,241
    cheers! Whats the down side if they are not in line vertically (i..e are leaning towards the chainset)? more wear, will break ?
    Road - BTwin Sport 2 16s
    MTB - Trek Fuel 80
    TT - Echelon

    http://www.rossonwye.cyclists.co.uk/
  • redddraggon
    redddraggon Posts: 10,862
    willbevan wrote:
    cheers! Whats the down side if they are not in line vertically (i..e are leaning towards the chainset)? more wear, will break ?

    Not a lot really, if the mech is slightly angled towards the chainset it means the chain is slightly shorter than ideal. As long as you don't use the big chainring with the bigger sprockets you should be fine (as long as it isn't far too short)
    I like bikes...

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  • Bugly
    Bugly Posts: 520
    the vertical orientation in big/little may work as a starting point but really you should consider the amount of slack and the stretch at the little/little and big/big ends as well. If you have a 53/39 chainset with a 11/21 vertical is fine if you have a triple or 50/34 with a 12/28 then the then you may have an issue with it.
  • aracer
    aracer Posts: 1,649
    redddraggon wrote:
    willbevan wrote:
    Quick questiion, if you change from a short cage mech, to a long cage, will the chain need lengthening?

    Yes, put the gears in big front, little rear, and the jockey wheels should sit in line vertically.
    That's just one method of determining chain length (the one suggested by Shimano for road bikes), and not necessarily the best for use with a long cage mech and/or a triple. The most important chain length issue is to ensure there is sufficient chain to wrap both big cog and big ring - though generally if you size like this you get a shorter chain than if you size as you suggest (with a short cage mech). If you are just changing mechs then there is no need to change the chain length - it's only if you are using a bigger cog that you might find the existing cage too short.

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