Hi, can anyone explain shimano’s latest crankset line up to me as I’m confusing myself with what I think I’m after.

What I would like is a replacement crankset (with a 34t chainring) to go onto my Chameleon when I build it back up with a new XT 1×12 groupset. I was going to try and re-use my old GX eagle crankset and chainring but decided I that it would annoy me if the parts didn’t match nicely.

The frame is set up with boost wheels and I’ve previously been running a boost GXP GX Eagle crankset/chainring combination with no issues; I think this has a chain line of 52 mm.

On shimano’s configuration compatibility checker they list the FC-M8100-1 as being compatible with a boost setup (148 mm O.L.D.) and also list the FC-M8120-1 variant as being boost compatible.

Shimano list the chainline for the M8100 as 52 mm and the M8120 as 55 mm, this would lead me to thinking that I should be fine with the M8100 as a replacement but then what is the M8120 (or indeed the M8130) for?

So, can anyone confirm that the FC-M8100-1 is likely to be a perfectly acceptable replacement for my existing boost set-up (i.e. I won’t end up jamming the shimano chainring into my frame because of clearance changes) or do I need to try and find a M8120 instead?

If your Sram is 52mm, then the 52mm from Shimano will fit.
I believe they intend 52mm to be for 135/142, 55mm for 141/148 and 56.5mm for 157 Superboost rear ends.
I fitted 152 to my 148 and it works a treat, but the new Shimano 12 speed stuff is way more tolerant of wide/wild chainlines due the the cage being angled (looks twisted) so that the cage angles in on big sprockets and out on small, making everything run way smoother than the comparatively clunky 11 speed stuff which was a lot less tolerant of wider chainlines.

Summary – 52 or 55 will both work. I went 52 – just because I could with the ring size I wanted. If I’d wanted a bigger ring size, I’d have gone 55 fir clearance.

Ok, I guess 52 mm it is then and I’ll keep my fingers crossed that it all fits when it arrives.

If ring size is the same, then no reason why not.

If your using the HG+ chain, you should use shimano 12sp chainring, for example a blackspire snaggletooth on my m8000 chainset just wont work.
I’ve read the single ring 12sp chainline is 52mm for 142 and 148 rear.