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Trying to put all this info together:
- On 135 and 142 OLD hubs, an 11s cassette has a 44mm chainline
- Looking at the SRAM Frame Fit PDF pointed to by Mark McM, Sram Red and Force road cranks have a chainline about 45mm (diagram is dimensioned to the inner face of the chainrings so I added 1 mm).
- Changing these cranks to a 120/80mm spider allows mounting of a 42T/28T pair that is a stock combo on SRAM 2x10 (either from SRAM or aftermarket)
- If current Shimano road double cranksets also have a +/-45mm chainline, it's possible that the Ultegra 11s front derailleur and Shimano 11s shifter (RS685, R8000, etc.) can shift this chainring set-up, which has a 14T differential, since Shimano makes the Ultegra crankset in 50-34, 52-36, 53-39, and 46-36, a range of 10T to 16T differential. The chain guide shape may not be optimal for the small diameter 42T chainring, and the bottom of the chain guide may hit the top of the chainstay.
- Getting the SRAM crankset with a GXP BB allows it to be fit to a 68mm BSA BB shell.
Did I get this right?
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