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  1. #1
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    Chainline and rear spacing question

    I have read so many forum posts but am still confused. I have 197mm rear spacing on my fat bike, am running a BSA120mm Bottom Bracket with spacers, and am currently running Race Face Aeffect for 190mm-spaced fat bikes with a Race Face chainring (0mm offset). This works great and the chainline is optimal (as far as I am aware).

    However, I would like to change to a SRAM crankset so I can run an Eagle chainring, but SRAM only makes cranks spaced for 170mm rear spacing. Can I still use a SRAM fat crank but then use a 6mm offset chainring and flip it around, or something? How does that work exactly?

    I'm working with direct mount/cinch chainrings and a 1x setup.

    Thanks!!

  2. #2
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    First of all, why do you want to change to an Eagle chainring? How will that be better than what you have now?

    Second, SRAM does make cranks for 190mm/197mm rear spacing frames. They are hard to find, expensive, and only come in carbon.

    As far as using a crank designed for a 170mm frame on a 190mm frame, it depends. First issue is BB width. What is the actual BB shell on your frame? You say you're using a 120 BSA BB with spacers, what exactly does that mean? If BB shell on your frame is 120mm BSA, you cannot use a crank designed for a 170mm frame, as they need a 100mm BSA or equivalent BB shell. If your frame has a 100mm BSA shell, than you may be able to use a crank designed for a 170mm frame. It will depend on the crank arms clearing the chainstays.

    I tried it on my Chumba, which uses a 100mm BSA BB shell and 197mm spacing. On that frame, an SRAM crank designed for 170mm would not clear the chainstays, but the Race Face crank designed for 170mm frame worked.

  3. #3
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    Quote Originally Posted by bikeny View Post
    If BB shell on your frame is 120mm BSA, you cannot use a crank designed for a 170mm frame, as they need a 100mm BSA or equivalent BB shell.
    Thanks, that's what I wanted to know. I do have a 120mm BSA shell, so that means I cannot fit any SRAM cranks that are not super-expensive and all-carbon. I'll be sticking with Race Face Aeffect/Turbine/Next cranksets. Race Face needs competition!

  4. #4
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    Yeah, it would be nice if SRAM made an aluminum version of their 190mm cranks.

  5. #5
    since 4/10/2009
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    RF rings and many others are compatible with SRAM's 12spd stuff. You won't get the Extra Special Eagle chainring teeth, but it will work fine.

    SRAM is missing a market by not offering its rings in other direct mount flavors.

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