Shimano XT cranks: Boost v. Non Boost- Mtbr.com
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  1. #1
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    Shimano XT cranks: Boost v. Non Boost

    Hi,

    I would like to run a 24-34 XT crank with an 11-42 cassette(11 speed) on a 27.5 bike to get the same low gear as a 26'er with XT triple: 22-34-Bash and 11-36 cassette(10 speed).

    The 27.5 bike has a boost rear. The XT boost double cranksets that are for sale come with a low of 36-26, so I want to buy the cranks separately and add the 24 and 34 chainrings. What is the difference between the boost XT crank only and the non boost XT crank only? For instance, these two:

    Non boost ($98): Shimano XT FC-M8000 Single Crankarms > Components > Drivetrain > Cranksets | Jenson USA

    Boost ($105): Shimano XT FC-M8000 Boost Crank Arms > Components > Drivetrain > Cranksets | Jenson USA

    Is the only difference a 1.6mm spacer that comes with the boost crank (50.4mm v 52mm chain line)? I assume I can add two chainrings to either crank. Is that right?

    Thanks.

  2. #2
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    I'm curious about the difference as well.

  3. #3
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    Anyone get this cleared up?

  4. #4
    RAKC Industries
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    This was one of those things that the OP answered his own question. The difference is chainline, thats it. And 1.6mm worth of difference. Basically halving the extra 3mm if boost 148 rear. May help with chain ring clearance (maybe able to go one size larger) Can used standard crankset as well with no ill effects.

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  5. #5
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    I'm still not clear on how the chainline is achieved in this guise vs non-boost? Is the extra width then just from a few BB spacers? I looked at Shimanos tech page and it did not mention different part numbers for either boost/non boost arms so I'm hoping spacers are the key here.

  6. #6
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    I believe the spider that holds the chainrings is further off centre I think boost model. It's not a spacer thing.

  7. #7
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    Quote Originally Posted by Dexter-01 View Post
    I believe the spider that holds the chainrings is further off centre I think boost model. It's not a spacer thing.
    That makes the most sense. That's how it is on road stuff (130 vs disc spacing).

  8. #8
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    do not want to start another thread. getting first boost frame this weekend, a Tallboy. Is it okay to use a non-boost crankset?


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  9. #9
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    In my experience, yes
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  10. #10
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    Quote Originally Posted by Dexter-01 View Post
    I believe the spider that holds the chainrings is further off centre I think boost model. It's not a spacer thing.
    I'm doing the XTR M960 1x cut/grind/polish mod with a 30t Oval snaggletooth so I no longer am worrying about the boost/non boost spacing.

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