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  1. #1
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    MRP 2x + Mojo HD = medium or long cage rd?

    After looking at my build kit, and riding style, I decided to trade my unbuilt Mojo SLR frame in for an HD140. My only real question is whether or not I need a medium or long cage RD for running 2x10 (XT 28/40 and 11-36) and the MRP 2x chain guide. Any thoughts?

  2. #2
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    Generally, you need medium cage lengths for 2x drivetrains and a long cage for 3x drivetrains.

    A 2x10 with 28-40 chainrings and 11-36 cassettes needs a cage length to handle 12+25=37 teeth. Shimano RD-M780 SGS XT long cage has a capacity of 43T and the RD-M780 GS medium cage has a capacity of 35T. I guess in this case you need the SGS model to be safe.
    2013 Ibis Ripley
    2012 Ibis Mojo SL-R
    2009 C'dale Rize 3

  3. #3
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    I asked the same question to my Ibis dealer when we were putting together my HD and he was adamant to stick with the long cage and not go with the medium. His reasoning was that as the suspension goes through its travel the chain stay length increases and you want to be sure to have enough chain to handle the growth.

  4. #4
    mountain biker
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    Quote Originally Posted by Nate3510 View Post
    I asked the same question to my Ibis dealer when we were putting together my HD and he was adamant to stick with the long cage and not go with the medium. His reasoning was that as the suspension goes through its travel the chain stay length increases and you want to be sure to have enough chain to handle the growth.
    and what does your derailleur have to do with the length of your chain at max compression? nothing. you want to set your chain length at max compression threaded through your derailleur on the biggest chainring/cog combo you will use. then you adjust your shifting. what the derailleur does is take up chain slack in small/small combos.

    I've been running a short cage derailleur (ss from Shimano) for years now 2x9 (on a triple in 26/32/bash configuration). I knew full well that the in the granny/small cog combo the derailleur doesn't take up the slack, but I never rode in that combo anyways. I just went 1x10 with a 11-36 cogset, 32 ring and clutch zee ss. The derailleur can't quite take up the slack from the 11t, so I've limited it out. I'm still trying to decide if that's a problem or not. ymmv.

    Anyways, my main point is the derailleur takes up slack in the smallest cog and/or chainring combo. chain length is determined by the big big combo with your bike at full compression, not your derailleur.
    continuous growth is the strategy of a cancer cell.

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