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  1. #1
    mtbr member
    Reputation: Grande's Avatar
    Join Date
    Feb 2004
    Posts
    177

    New question here. 2X9 - BB spindle length / Shimano BB road vs Mtb

    so:

    I plan on going 2x9 on my 29er using a XTR m952 crank standard 110/74. Plan on using a 26or28/38 setup to start. Since teh crank is XTR I have to use Octalink V1. Standard BB spindle is 112.5 but 116mm is available. However I could use a DuraAce or Ultegra or 105 to get a 109.5.

    My questions are:

    1. Is it preferred to run rings on the inner and middle over middle/outer in a 2X9?

    2. If so, assume I spend most time in the inner (26 or 28, or maybe 30) do I have to accommodate for that by adjusting the crank outward (by the BB spindle length)?

    3. If 112.5mm is not the best option can I used a Shimano road BB. I'm not asking if it will work. But how well will it work. Will dirt and mud kill them?

    thoughts?

  2. #2
    Former Bike Wrench
    Reputation: mtnbiker72's Avatar
    Join Date
    Jan 2007
    Posts
    15,985
    Well, there is no way you can run your desired setup using the middle and outer chainring positions. You simply cannot get much smaller than a 34t on a 110 5 bolt pattern. So, you will be running the granny/middle chainring places. Your not going to want to go any narrower than the 112mm spindle to maintain a 47.5 chainline...you may want to go 116mm to go a little wider since your only using the inside and middle chainring positions.

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