Shimano XTR 9 speeds RD-M970 rear derailleur & XTR 9 speeds 11-34T cassette ???
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  1. #1
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    Shimano XTR 9 speeds RD-M970 rear derailleur & XTR 9 speeds 11-34T cassette ???

    I have a Shimano XTR 9 speeds RD-M970 rear derailleur(short cage) and would like to use it for a XTR 9 speeds 11-34T cassette.

    Is it a workable combo ? Or do I need a RD-M971 instead ?

  2. #2
    'brifter' is f'ing stupid
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    Quote Originally Posted by edle View Post
    I have a Shimano XTR 9 speeds RD-M970 rear derailleur(short cage) and would like to use it for a XTR 9 speeds 11-34T cassette.

    Is it a workable combo ? Or do I need a RD-M971 instead ?
    Max cog is 34, so that's good. Capacity is 33, so you need to figure that out.
    #promechaniclife

  3. #3
    Carbon Fiber = Explode!
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    When it comes to MTB derailleurs, never buy short cage.
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    Quote Originally Posted by cxwrench View Post
    Max cog is 34, so that's good. Capacity is 33, so you need to figure that out.
    'Capacity is 33'....Do u mean the front chainring max. is 33T ?

  5. #5
    'brifter' is f'ing stupid
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    Quote Originally Posted by CleavesF View Post
    When it comes to MTB derailleurs, never buy short cage.
    That's just stupid. If the spec is correct for the application, why not?

    Quote Originally Posted by edle View Post
    'Capacity is 33'....Do u mean the front chainring max. is 33T ?
    No..."capacity". The difference between the small cog/large cog + the difference between the small ring and large ring. For example:
    11/34 cassette: difference is 23 teeth
    50/34 compact crank: difference is 16 teeth
    23 + 16 = 39 which is obviously more than the capacity of 33 for the GS short cage derailleur. You'd need the SGS long cage, which has a capacity of 43.
    If you were running a single chainring you'd be fine w/ the GS and it's shorter cage, contrary to the incorrect advice provided by the other guy i quoted.
    #promechaniclife

  6. #6
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    Quote Originally Posted by cxwrench View Post
    That's just stupid. If the spec is correct for the application, why not?



    No..."capacity". The difference between the small cog/large cog + the difference between the small ring and large ring. For example:
    11/34 cassette: difference is 23 teeth
    50/34 compact crank: difference is 16 teeth
    23 + 16 = 39 which is obviously more than the capacity of 33 for the GS short cage derailleur. You'd need the SGS long cage, which has a capacity of 43.
    If you were running a single chainring you'd be fine w/ the GS and it's shorter cage, contrary to the incorrect advice provided by the other guy i quoted.
    Thanks for the valuable input.
    Yes, I'm planning to run a single ring(28T or 32T) in the front.

  7. #7
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    970 is Rapid Rise, 971 is regular small cog normal.

    If you are sure you have a 970, then get a 970 with a longer cage, not a 971.

    I use a 971 short cage on my commuter. 44/30 985 crank and 12/27 DuraAce cassette. Works great.

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