i live in salt lake city and run 36 x 20 on my sass, which is pretty hard on sustained climbs of which there are many. i tried many combinations in the 1.65:1 to 2:1 range, as does everyone, 32/16, 17, 18 and 19 and 34/18, 19 and 20 and so on...36/20 runs the drive train smoothest for me and i just have to work harder which is kind of the point for me. luckily, my experimentation in gearing has left me with a sizable collection of cogs and rings, so when we travel, i can easily adjust to new conditions, though so far, few areas have been stouter than home. i have a fixed mtb commuter as well and i run 38 x 14 and live in the foothills where i use the pedal momentum as "power assist" on climbs.
marc
oops, didn't see the last thread about clearance, sorry...up to 38t in the front doesn't seem to matter to much and wrt drivetrain wear, mo' teeth seems better...