How do I determine proper chainline?-
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  1. #1
    mtbr member
    Reputation: crawdad's Avatar
    Join Date
    Jan 2004

    How do I determine proper chainline?

    I know, I know...not another chainline question. But I did some searches and I couldn't find a thorough explanation of how to measure the proper chainline.

    Just finishing building up a 2005 Unit, and I'm pretty psyched. All chainline adjusting will happen on the hub - it's a Shimano 9-speed cassette, Rennen threaded spacers, and a CK Cog. No problems yet, I'm just wondering if there's a good way to do it right the first time.

    Thanks in advance for any help.


  2. #2
    mtbr member
    Join Date
    Mar 2005
    Mount the front chainring wherever you want on the crank and then install the crank and chain on the bike. Then take a straightedge across a couple flat spots on the crank spider and move the rear spacers around until the chain is parallel to the straightedge.

  3. #3
    mtbr member
    Reputation: mckeand13's Avatar
    Join Date
    Nov 2004
    Another easy way is to put the cog on with no spacers or lockring. pedal the bike on a stand a little bit. The cog will drift to the spot that the chain "wants" it to be in. Make a mark on the freehub body and then put your spacer on until they meet that mark or close to it. Put the cog on, the rest of the spacers, and then the lockring. Ta-daaa.
    It's only weird because it's not normal.


  4. #4
    mtbr member
    Join Date
    Nov 2005

    Good job! Sheldon knows how!

  5. #5
    mtbr member
    Join Date
    Jan 2004
    Eyeball it.

    I've got a road SS, a road fixie and a MTB SS. I've eyeballed every one of them and never had an issue. It's not rocket science. As an alternative use the straightedge method.

  6. #6
    thump thump
    Reputation: artbeat's Avatar
    Join Date
    Dec 2005

    tips from the Endless Bike site

    For a golden chainline:

    1. Measure in millimeters (inches times 25.4) the distance from your chain ring to the dead center of the seat tube
    2. Subtract this distance from 70mm (~.75") if using a Kick Ass Cog, or subtract from 67mm for a cheap steel cog
    3. With the rear wheel in the dropouts and nothing on the free hub body, make a pencil mark on the free hub body exactly the calculated distance in from the inside right hand dropout face.
    4. Install spacers onto the free hub body up to the pencil mark
    5. Install your cog, additional spacers, and the lock ring
    6. Go out and ride on the smoothest drive train you have ever felt!
    "What is truth?" - Pilate to Jesus

  7. #7
    mtbr remember
    Reputation: racerx09's Avatar
    Join Date
    Dec 2004

    Straight as an arrow...

    I got tired of measuring, eyeballing and etc... I took an arrow and held it flush on the inside of the crank chain ring. I take my spacers and fill up the hub until the inside of the cog is also flush against the arrow.

    Perfect everytime!

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