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  1. #1
    mtbr member
    Join Date
    Feb 2009

    Another rear chainline thread. Need help.

    Need some help here......

    Front chainline is 51mm or 50mm using Shimano's measurement technique. This matches my XTR derailleur specs of 50mm.

    Rear chainline by all my measurements is 44????
    The rear frame between the dropouts is 135mm. Divided in half is 67.5. Measured my cassette width to be 35.56mm. Divide is half = 17.78. Space between dropout and cassette is 5.842mm. Therefore 17.78 + 5.84 = 23.66. 67.5 - 23.66= 43.84mm.
    This is the calculation I used to measure from the centerline to the center of a 9 speed cassette. What am I doing wrong??


  2. #2
    Keep on Rockin...
    Reputation: Miker J's Avatar
    Join Date
    Nov 2003
    Provided your measurements of your cassette and the space b/t the cassette and dropout are correct the math does not lie.

    Seems to me like cranksets have been pushing chainlines outboard over the years. Probably has to do with larger mtb tires, leading to wider chainstays, requiring more ring and crank clearance. Plus the new outboard bearing cranksets push the crankset outboard. All the more reason to go with an wider rear spacing standard a just make a dishless rear wheel.

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