I would seriously doubt it's in the arms. Consider all the lengths Shimano offeres cranks in and you think they'd make special ones for a narrower Q-Factor.Is anyone able to comment on the difference in frame clearance (if any) between the XTR M9100-1 crank and the M9120. The M9120 is supposed to have 168mm q factor, but 9100 is supposed to have 162. Not sure if this is achieved by a thinner crank, or if the cranks arms have less angle, or are otherwise closer to the frame.
I have a boost frame with a reasonably wide set of chainstays, so am not sure if it'll clear or not (i currently have XT M8100, which are quite a bit wider with 172 q factor). If the internal face of the crank was simply closer to the frame by the difference in q factor, it would be easy to calculate, but not clear if the cranks are the same thinckness.
A technical drawing of the cranks would obviously make clear, but haven't been able to find one of those anywhere.
Thanks to anyone who can help!
The most cost effective way is the spindle.