By calculation, I should be using 195's, but choosing to err on the side of caution, bought a set of Zinn 190 cranks. When I put them on my road bike, I grounded a pedal in a turn, so moved them to my MTB, and now they work good. I have settled on 180's for my road bikes, and can feel the difference from the 175's I had before. I can pull one higher cog with the 180's with the same perceived effort. YMMV