Quote:
Originally Posted by Nomadmax
I've grown to like the 32/48 so I may look at the Shimano GRX 12 speed double in 31/48. I have a Lynskey with the 11 speed version and like it a lot. I'd need a set of T47 BB cups and a GRX FD as well. If I decide to go that route, I'll need to figure out if the GRX has a wider Q factor and if the otherwise Campagnolo Chorus 12 drivetrain, specifically the shifters and RD will work with a setup like that.
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This part is easier: Yes,
Shimano 12spd GRX cranks have a wider chainline and Q-factor than
Campagnolo Chorus 12spd cranks. Specifically, the GRX cranks have a chainline of 47mm and a Q-factor of 151mm, whereas the Chorus cranks have a chaline of 45mm and a Q-factor of 145.5mm.
Campagnolo cranks have a narrower Q-factor than most other road cranks, and that is likely causing part of the clearance issue. If the 172.mm have more clearance than the 170mm cranks, then there is likely a manufacturing variance between the two cranksets - but is the 170mm crankset narrower than spec., or is the 172.5mm crankset wider than spec.? You'll have to measure both cranksets to know for sure.
Others have likely gotten the GRX cranks to work with a Campagnolo drivetrain, but the chainline might not be optimal. These days there are plenty of other sub-compact options to consider.