Good evening,
I am currently building up a new bike and have found myself with the following question that I am strugling to Google my way out of. That is as follows:
What is the difference between Shimano XT m8000 vs m8100 vs m8120 boost cranksets?
The m8000 look slightly different to the latter 2 but is there any reason to pick or avoid any of these? The chainline measurements appear to differ slightly, ableit a millimetre or 2, despite all being labeled as boost. A follow on question is are the chain rings interchangeable between these chainsets? I hope I’m making a mountain out of a molehill or the singletrack knowledge base will be able to guide me away from disaster. Many thanks in advance!

Links to the M8000 , M8100 , M8120 cranksets

They are all good. M8000 is the old model with a four bolt chainring that limits you to a 30T cog as smallest. The m8100 series have a different way of mounting the chainring, which needs a special tool. As long as you get a boost one it will fit. However it depends on the frame whether a non boost will fit – I had a non boost one on a Bronson and it worked perfectly. They’re the best cranks for their price I think. But SLX are good too but the chainring is heavier on those.

Thanks! they all look similar in the pictures, as they all have spiders rather than a centre lock system. I assume that there is an advantage of the newer system. Is this just a few grams of weight? From my standpoint, the requirement of specialist tools is a disadvantage and a barrier to a self build.

M8000 are for 11 speed chains, M8100 and M8120 are for 12 speed (though may work ok with 11 speed chains). The chainrings are not interchangable as the 12 speed ones are direct mount and require a specific tool.

think this has squared up the rest! Thanks for info, now I’m thinking I should return my m8000 blackspire chainring and get the direct mount system despite the direct mount tool situation in an attempt to future proof the build for chainring replacement givent that the blackspire 12sp m8000 may not be available in the future.

M8100 / 8120 crankset comes with tool for direct mount ring, be foolish not to future proof with m8100. I’ve got m8000 and options are running out for aftermarket rings that work with 12sp hg+ chain.
M8100 52mm chainline.
M8120 55mm chainline.