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So new frame is boost, and my old kit I want to use is non boost. New frame has a 73 mm threaded BB. I was thinking if I used two 2.5mm spacers underneath the cup (rather than the 1 that is required) I would be close enough? XT cranks have 3 mm difference in chainline between boost and non boost so I would technically only be off by 1/2 mm. Does this theory hold true?

Thanks

Jason
 

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So new frame is boost, and my old kit I want to use is non boost. New frame has a 73 mm threaded BB. I was thinking if I used two 2.5mm spacers underneath the cup (rather than the 1 that is required) I would be close enough? XT cranks have 3 mm difference in chainline between boost and non boost so I would technically only be off by 1/2 mm. Does this theory hold true?

Thanks

Jason
The only difference between a boost and non boost crank is the chainring.
 

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So new frame is boost, and my old kit I want to use is non boost. New frame has a 73 mm threaded BB. I was thinking if I used two 2.5mm spacers underneath the cup (rather than the 1 that is required) I would be close enough? XT cranks have 3 mm difference in chainline between boost and non boost so I would technically only be off by 1/2 mm. Does this theory hold true?

Thanks

Jason
No. the thickness of spacers you use is determined by the bb shell of your frame and the length of your crank spindle. Put more spacers on than the specs dictate, and you're going to incorrectly preload the bb bearings, have an incorrectly tightened crank interface, and have a crank that doesn't have enough contact between the spindle and the crank arm with the fixing bolt.

On Shimano cranks, the difference between boost and non boost is with the crank spider.

You MIGHT be able to use your non-boost cranks on your boost frame without any fiddling as long as the frame has clearance for the narrower chain line. Some frames do. There are a number of people who do that.

The only difference between a boost and non boost crank is the chainring.
no. SOMETIMES, that's true (SRAM, RaceFace, looks like the newest direct mount Shimano is prob that way). Sometimes, the difference is the spider (older Shimano, RaceFace CINCH 2x spiders). Sometimes, the difference is the spindle (RaceFace). Sometimes, the difference can be EITHER the chainring, spider, or spindle (RaceFace).
 

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^^^I intentionally run a non-boost crank on an otherwise boost bike. The difference in chain line is 3mm so slightly favors the larger cogs where I spend most of my time laying down power. It's also a little less prone to coming off the big cog when backpedaling. Shifting is unaffected as it's the derailleur pulleys that control the chain feeding onto the cogs.

If you have the non-boost crank and clearance to run it, try it.
 

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^^^I intentionally run a non-boost crank on an otherwise boost bike. The difference in chain line is 3mm so slightly favors the larger cogs where I spend most of my time laying down power. It's also a little less prone to coming off the big cog when backpedaling. Shifting is unaffected as it's the derailleur pulleys that control the chain feeding onto the cogs.

If you have the non-boost crank and clearance to run it, try it.
agreed, to me this seems better for chain life. and better shifting on the larger cogs.
 

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I've gotta similar question so thought I'd pile on here.

I've been running a SRAM XX1 DM GXP Crankset with 168 Q Factor on a non-Boost 2016 Tracer with a SRAM 10-42 cassette.

Just bought a Boost 2018 Mach 5.5 with a Shimano 11-46 cassette and I'd like to swap the XX1 Crankset over.

Both bikes have BB92 so should be an easy swap but what kinda offset on the DM Chainring is gonna get me close to the 53mm chainline recommended by Pivot?

Options I'm seeing are 0mm, 3mm, or 6 or 7mm.

Thanks
 

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I've gotta similar question so thought I'd pile on here.

I've been running a SRAM XX1 DM GXP Crankset with 168 Q Factor on a non-Boost 2016 Tracer with a SRAM 10-42 cassette.

Just bought a Boost 2018 Mach 5.5 with a Shimano 11-46 cassette and I'd like to swap the XX1 Crankset over.

Both bikes have BB92 so should be an easy swap but what kinda offset on the DM Chainring is gonna get me close to the 53mm chainline recommended by Pivot?

Options I'm seeing are 0mm, 3mm, or 6 or 7mm.

Thanks
How are you fitting your wheels to this new bike? If you are using the 3mm spacers on each side+3mm disc spacer, then your cassette is exactly where it was before, no boost spacing on the crankset necessary. Just need to adjust the derailleur limit and cable. If you are using a boost hub, now your cassette is 3mm further outboard. You'd want to move the chainring 3mm outboard.
 
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