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  1. #1
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    M985 XTR Race crankset -Any chainrings smaller than 40/28 combo?

    I'm buildling a 29er hardtail and thinking of entering the world of 2 x 10. I'm also sold on the 172.5mm crankarm length. The potential issue is that only the XTR M985 Race crankarms are available in a 172.5mm length (the Trail version is available only in full sizes?), and the smallest chainrings I know of are a 40/28 combo. May smaller chainrings fit the Race version? Thanks.
    It's not dirt in my apartment --it's Earth.

  2. #2
    whistler
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    shimano uses a proprietary 88mm BCD on their 2x10 "race" XTR cranksets, so (as far as i know) only their chainrings will fit, and 28/40 is as low as they go.

    2x10 XT and XTR "trail" cranksets are available in 26/38, but they use the "older" standard 64/104 BCD, so the rings wouldn't fit new XTR race (not that the rings are separately available yet anyway).

    SRAM, raceface, and other use 80/120 BCD for their 2x10 cranksets, and seems like most aftermarket rings are following suit with this sizing.

    is 172.5 really that important? if you're really short, get 170. otherwise just get 175mm and don't worry about it, then you're not cornering yourself.

  3. #3
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    Thanks for the input. I ended up going 40/28 XTR 172.5 on the front, and paired it with a 36-11t cassette on the back. ...No problems at all on the hills here for XC riding. There have been a couple times on short steep hills when I found my easiest gear still a tad too tall; then again, half my riding group was walking the same part of the hill.

    ...I love the 172.5mm! 170mm was too short, and haven't tried 175mm since the mid nineties.
    It's not dirt in my apartment --it's Earth.

  4. #4
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    Any updates on aftermarket chainrings smaller than a 28 for the M985?

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