I'm 6'1", run my saddle at 80cm from BB, and use 170's on my fixie - I haven't used 175's on it, but I do have 175's on my mountain bike and 172.5's on 3 road bikes. Honestly, I cannot tell the difference between any of them after a couple of pedal revolutions...perhaps if you rode 30 miles on 175's then jumped directly on 170's you'd feel a difference but I'm thinking in real life you won't even notice. 180 rpms? Nice cadence; I'm still trying to top 170.