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

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


    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?


  2. #2
    Former Bike Wrench
    Reputation: mtnbiker72's Avatar
    Join Date
    Jan 2007
    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 may want to go 116mm to go a little wider since your only using the inside and middle chainring positions.

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