Piggy-backing off that last post: since my fixed-gear conversion runs a mish-mash of parts (Surly cogs but a Sugino GLP road crank and "road" 45T or 42T ring depending on the season) there is some tension variance. I "characterize" it by installing the chainring so that the tightest point is with the drive-side crank arm pointing forward. That way, if I have to fix a flat on the road, I can point that crank arm forward when reinstalling the wheel and the chain won't get any tighter than that while riding.
