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  1. #1
    lookin' for a hill
    Reputation: nikwashere's Avatar
    Join Date
    Mar 2008

    air9carbon bb30 cups in SIR9?

    what is the diameter and width of the bottom bracket shell in the air9 carbon? I have heard about the Bb30 inserts for the air9 carbon and was considering the possibility of inserting some into my SIR9 for a bb30 XX build. I'm sure there is something which will keep me from doing this, but just curious. Maybe Sram will eventually make a press fit big enough.
    anyone out there try to machine their own set of BB30 cups for a sir9? I have not seen the bb30 cups in person except for a quick look at interbike, so am unsure exactly how they are shaped.

  2. #2
    mtbr member
    Reputation: Niner Bikes's Avatar
    Join Date
    Dec 2004
    Actually, the diameters of the two shells are identical. The issue will be derailleur alignment. Since the SIR 9 was developed before the A9C, the seat tube is aligned in such a way that it's designed to have the EBB in the forward most position (3 o'clock when looking from the driveside) to line up correctly with a front derailleur. The CYA BB30 cups are not off-center, like an EBB, but rather on the center axis of the bottom bracket shell. This will alter the alignment of the front derailleur a bit, but may still be possible. We haven't fully experimented with this on the SIR 9 yet. Do you have a bio-centric EBB on your SIR 9? Contact me through Niner (877) 646-3792, and let's talk about it.

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  3. #3
    mtbr member
    Join Date
    Apr 2009
    I'm also interested in doing this. Did you ever try it?

  4. #4
    4 Niners
    Join Date
    Dec 2008
    I have a Sir9 that I run the EBB in the 11 O'clock position so all the geometry will match my other SIR that is SS. It shifts great (X9 shifters XT front der). The other issue you are going to run into is clearance between the chainstays and the teeth of the chainrings. It is close in my setup and will probably be close using BB30 since most of those cranks have narrower "Q"

    It is too bad that they can't even offset the BB30 even a MM. It would allow SS with a magic gear and allow for chain stretch.

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