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I am interested in swapping the 2x9 group on my cross bike to a 1x11 group. I was looking at my crankset options and it appears that SRAM Rival 1 and Force 1 seem to be the primary options. I was wondering if mountain bike cranksets would also be compatible. Not sure which route I was planning on going, but it would definitely give me more options if I could also shop single ring MTB crankests. Thanks
 

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I have done it, for another reason. My cross bike didn't have low enough gearing for the trails I was doing.

Swapped a GXP 50/34 for a Deore 40/26 and Deore FD.

Deore came with a BB and spacers.

Wider Q factor obviously, which didn't bother me.

All fine.
 

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In case the rear dropout spacing (O.L.D.) of your cross bike is 130 mm, a Mountain crank set might not be ideal with respect to the chain line. (That means it might work though, but there is an elevated risk of issues.)

As far as I know, SRAM are currently offering crank sets for the following specs:
MTN 135 OLD (traditional)
MTN 148 ("Boost")
ROAD 130 OLD (traditional)
ROAD 135 OLD (typically disc brake)

The differences are due to spindle length, curvature of crank arms and/or offset of chain ring.

Dependent on whether you need the GXP or 'BB30' spindle, there could be implications on your bottom bracket setup.

In short: I'd try to avoid mixing ROAD and MTN - if it has to be, figure it out carefully.
 

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I contemplated the issue of chainline when doing my swap.

Shimano supplies 3 x 2.5 mm spacers to use with a 68 mm BB shell, so it is easy to get the correct chainline for a CX frame with "road" dimensions.
 

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The spacers are for the rings on the spider, or the bb spindle? Spacers on the BB spindle might move the entire crank left or fight, and it may not wind up centered.
 

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The spacers are for the rings on the spider, or the bb spindle? Spacers on the BB spindle might move the entire crank left or fight, and it may not wind up centered.
The spacers are for the bb cups. One will take up the space that exists when not using an e-type front derailleur and you'd use the other 2 if your frame is 68mm not 73.
 

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I started trying to explain, but @CX has done a much better job.

On a MTB with a 73 mm shell, a 2.5 mm spacer is used behind the DS cup. The chainline is correct for a MTB cassette which happens to be 2.5 mm further to the right than on a road bike. ((135-130)/2).

Therefore if the same spacer is used on the DS of a CX BB which is 2.5 mm closer to the centerline ((73-68)/2) it maintains the same relationship to the cassette which is also 2.5 mm closer. The other 2 spacers went on the NDS.
 
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