Single chainring crankset - need advice!

[Fatmat]

Hello. I’ve clearly no idea what I’m doing! I noticed that the axle/spindle was quite long, I offered up a standard MTB BB, I’m left with a lot of space, is this a Boost axle? Will it work on a standard MTB with spacers? Any advice would be greatly appreciated

 

[clubby]

What crank? That looks like a lot of extra axle. Any chance they are fat bike cranks? They were designed for a 100mm bb shell.

Boost generally uses the offset of the chainring to give the correct chain line.

 

[Fatmat]

Hi clubby, thanks for your reply. It’s a race face ride cinch. I think the spec is 137mm but actually measures 135mm (unless I’m measuring wrong). 137 seems to be quite a common size but ‘fat bikes’ did crop up when researching!

 

[Twozaskars]

Just took that measurement from my XTR M980 and it's 115mm.

 

[Fatmat]

Yes, this looks to be about 20mm to wide!

 

[Fatmat]

The best explanation for measuring a spindle that I can find is ‘the length + 5mm’ which makes sense as this is supposed to be a 137mm and I can make it measure 132mm if I ignore the 3 small pre-installed spacers. So I guess my question now is what setup does a 137mm spindled crankset work on?