Anyone seen/heard if there is an XTR crankset for Superboost? I have seen an XT version online but can't find any XTR version. Have a Pivot Trail 429 and am keen to swap out the RaceFace one for XTR.
Thanks in advance!
Shimano doesn't have a superboost version of the XTR cranks. Furthermore, both the FC-M9100 and FC-M9120 cranks both have a chainline of "only" 52mm.
In contrast, the XT and SLX models have three options: 52mm (FC-M7100/M8100), 55mm (FC-M7120/8120) and 56.5mm (FC-M7130/M8130).
A "hack" might be viable to adapt the M9120 cranks for nearly Superboost chainline.
There is a spindle spacer intended for the non drive side, but the dealer manual says is "can be shifted to the drive side crank if needed for clearance". They don't spec the thickness of this spacer, but I'll venture a guess its ~ 2mm. So move that to the drive side and you've now got a 54mm chainline. Next, obtain a 1mm spacer for the press-in BB, and add that to the stock 2.5mm on the drive side (this causes the spindle to protrude 1mm less than intended on the non drive side, but I've found that is within the tolerance on Shimano setups). Now you've got 55mm chainline. That should work w/ the 157mm rear, *assuming* that your crank and chainring are clearing the chainstay, and that you don't care about your crank arms now being asymmetric relative to the BB / bike centerline.
I did a similar hack on my Switchblade three years ago so I could run a boost XT 2X crankset. Drivetrain has been great for several years, no issue. But back then I didn't have the various options you do today.
If I were you, I would forego the XTR in favor of XT and perhaps even use the M7120 55mm version, which will save a few mm of Q factor and arguably improve your chainline and reduce backpedaling issues. Again, assuming your ring clears. I'm sure 32T or smaller is no issue.
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