I use my road bike (caad8) as a touring bike, and I feel I need lower gears. Today I'm using 50.34 compact road crankset, paired with a 12-27 road cassette (10v).
I'm considering a double mountain crankset, a 40.28 Shimano XT or Sram x5 42.28, to replace the UltegraSL I have.
I'd leave a pair of pedals on each crankset: courrent road pedals to the 50.34 and mountain pedals to the 40.28.
The question is: Will this worK? I mean, will It shift properly? I'm worried about the FD performance.
I don't want triple drivetrain because I don't want to change STi (limited budget)
This is an alternative to 10s mountain cassette, with big jumps between cogs that I don't like. A 11-34 may be, and changing RD to a shimano preshadow 9v. And longer chain of course.
How much lower do you need to go? By changing to an 11-28 cassette and a 33 inner you'll be almost as low as you'd be on 30x27 with none of the fuss of swapping out cranks, BB & pedal system. Nor would it be necessary to readjust the front mech.
I ride with a semi-fused ankle but manage fine with a 34x25 unladen. Of you're climbing with panniers then a triple may be a better solution.