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  1. #1
    mtbr member
    Reputation: Slyp Dawg's Avatar
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    Oct 2007
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    Calling all Middleburn Duo ISIS/Square Taper users: chainline to INNER chainring?

    I've got an ISIS spline set of Middleburn RS7s running on a 113x73mm BB, and I am having a hell of a time getting the chainline anything close to the middle of the cassette without needing 7mm worth of spacers (calculated chainline to the middle of the cassette is ~43.5mm as per the calculations on Sheldon Brown's website), and I've been looking to put a smaller chainring on it (currently have a 32t). I know the Duo offsets the inner ring in a bit to give a 50mm chainline for the two chainrings, but nobody seems to have ever mentioned how much offset that amounts to. I tend to spend a lot of time in the lower gears (1-5 when climbing with a 32t and frequently end up mashing 1st up hills) so I'd like to bias the chainline towards the middle or lower end of the cassette, would I be able to get anywhere near a ~44-46mm chainline running just a Duo inner ring/spider? I'm fairly confident I won't run into chainstay clearance issues with that low of a chainline and a fairly small chainring (27t or 29t), my main concern is actually being able to get the chainline in where I want/need it to get good shifting performance in the lower gears
    Quote Originally Posted by teamdicky View Post
    My butthole would pucker and invert until I was inside-out before I got to the bottom.

  2. #2
    Keep on Rockin...
    Reputation: Miker J's Avatar
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    Nov 2003
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    Can't give u numbers but when I ran a Duo with the same setup, I had no problems shifting in the low gears.

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