I switched from 170 to 165s on my road bikes a few years ago upon the advice of my fitter. For me, the difference was a marginally better power output with the shorter cranks. When my foot got to the top of the pedal stroke with the 170s, I had a small “dead spot” in which my power dropped off, I just needed to lift my leg a little too high.

I don’t like the feel that of 170s on the road bikes, I just feel like my pedal stroke if off, a little jerky-feeling. So when I got the TT bike, I went with 165s too.

As weird as the 170s feel to me on the road bikes, the mountain bike came with 170s and that feels totally fine.