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  1. #1
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    Determining Rear Der. length

    I've got a SRAM X.9 rear derailleur that came on my bike and I'm trying to figure out the length of the cage as I've decided to run my XT and sell it. Anyone know how to measure for length, or can anyone measure their medium cage and tell me how long it is from center of the bottom cog to the center of the middle cog (next cog up)?

    Thanks!

  2. #2
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    There is some super fancy method for determining what length you want. But to keep it easy, if you run the standard three ring crankset, you should run a long cage. Two ring, medium cage, one small ring, short cage. I'm sure someone is going to come behind me and do the super math, but this keeps it simple. Most mountain bikes run a long cage because most are 3x9.

  3. #3
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    Thanks mlepito, I saw that in an article.

    I'm actually trying to figure out the length of the der. I've taken off so that when I sell it I'm listing it correctly. But I appreciate the response!

  4. #4
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    I see. Well if it came with the bike, then I bet it's long cage. So you can sell it like that. Or, just don't list the size if you aren't sure. Put a pic on here. I might be able to tell by looking at it.

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  6. #6
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    Josh...came stock on your bike?
    what kind of bike?
    you may be able to look around (bikepedia, mfr.s website etc) and get a feeling of what 'cage' derailleur was spec'd

    It could be just me, but that cage looks like the long variety...easier for me to tell when its mounted on the bike and under tension
    Honestly... ahh I give up

  7. #7
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    Quote Originally Posted by highdelll
    Josh...came stock on your bike?
    what kind of bike?
    you may be able to look around (bikepedia, mfr.s website etc) and get a feeling of what 'cage' derailleur was spec'd
    Picked up an IH MKiii Comp from rscycle.com on sale. Swapped over some parts for my girlfriend from my old bike and am selling the new take off's. I looked around for what they spec'd it with on the sites but couldn't find a size. It does run a 3-ring x 9 so I know it's at least a medium cage, but seems shorter than a large.

  8. #8
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    that's a large cage.
    Oh noes. I'm going to drink the Kool-Aid.

  9. #9
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    If you took it off of a standard issue mountain bike then it's a long cage.

  10. #10
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    That looks like a long cage. You know you have to switch out the shifters too?

  11. #11
    ~Disc~Golf~
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    Quote Originally Posted by mlepito
    That looks like a long cage. You know you have to switch out the shifters too?
    depends on his shifters... sram makes both 'pull-ratios'
    I run sram twisties w/ xt mechs
    Honestly... ahh I give up

  12. #12
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    not fancy at all

    Quote Originally Posted by mlepito
    There is some super fancy method for determining what length you want.
    The way to figure it out is very simple.
    First, subtract the number of teeth in your smallest chainring from your largest.
    Second, do the same for your cassette.
    Third, add the numbers.
    Fourth, up to 45, long; up to 37, medium; up to 30, short (XO only).
    Example:
    Front: 44-22=22
    Rear: 34-11=23
    Total: 22+23=45, long, DONE!

  13. #13
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    But he is running a x-9 which only uses one ratio, and it's not what the xt runs. FYI if you are doing this for a shadow RD, don't bother. It an't all that.

  14. #14
    ~Disc~Golf~
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    Quote Originally Posted by mlepito
    But he is running a x-9 which only uses one ratio, and it's not what the xt runs. FYI if you are doing this for a shadow RD, don't bother. It an't all that.
    AHH!!! how short-sighted of me!
    I forgot to follow logic... X9 mech = 1:1 shifter (sram) vs. sram shifter* = either/or 2:1(shimano mech) ; 1:1 (sram mech)
    I should know better

    thanks for lookin' out

    *-Different shifters required of course
    Honestly... ahh I give up

  15. #15
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    good catch, mlepito. i was thinking about the hanger and his other plans didn't register. as far as i know you can never swap a sram rear derailleur for shimano w/out changing shifters. i think sram only makes derailleurs with the 1:1, so any sram shifter paired with a sram derailleur will be 1:1 and won't work w/shimano (2:1).

  16. #16
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    Thanks for looking out and for the input!

    As far as the shifters go, I actually swapped out most of the new bike for parts from a hardtail I had so she's setup with shimano shifters and der's.

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