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a 7800 front derailleur should be able to shift a XT 737 crankset when there are only two rings and it’s being operated by a road shifter?
Define "comfortably". The smallest outer ring in the 7800 series was 50T, that's a 12mm bigger radius than a 44T.
It would probably work if the chainline was right, but it wouldn't be pretty and there's a higher than normal chance of throwing or jamming the chain.The chainline is is a separate issue. In theory, the M737 middle ring is at 47.5mm, but the 7800 outer is at 47.5mm. If you wanted to get the chainline on an MTB crank to replicate that of a road crank, you'd actually use the inner and middle positions, not the middle and outer. An FD-7800 is probably never going to reach the stock outer ring on an FC-M737, and if it does it will be so far into the arc of travel that it's going downwards rather than sideways when you initiate a downshift.
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gbj_tester
@Eeyorecore
What’s the smallest ring a 7800 front derailleur can comfortably shift? 44-34 should be ok, no?
And with the different cable pull between rd and mt front derailleurs, that’s more of an issue between the small and middle cog on mt cassette, correct? A road front derailleur should be able to shift between the big ring and middle ring on a mt crankset?
So boiling down my stupid questions, a 7800 front derailleur should be able to shift a XT 737 crankset when there are only two rings and it’s being operated by a road shifter?