A revival of a dormant thread, but worthwhile I hope.
My Le Jeune track bike as I bought her, and as she is now with new wheels, saddle, stem, bar, pedals and brake caliper. (Why do so many people building single speeds or fixies set them up with only a rear brake? Around 80% of your braking power comes from the front brake, and I've yet to launch myself over the bars, even during hard emergency braking!)
She's running 42/16, and I managed a 3:42 Argus in the rain earlier this year.
Dividing the number of teeth on the chain ring by the number of teeth on the freewheel or sprocket gives you a number that you can use as a basis for comparison of all other gear ratios.
My 42/16 ratio works out to 2.625 and has been a manageable (not easy) gear for climbs and flats around Cape Town. (You can get close to this number with lots of other ratios, including 53/20, which works out to 2.65, or 39/15, which works out to 2.6. This is handy if you're building up a single speed or fixie with a road crank.)
The Rook bikes, and quite a lot of the other single speed / fixie companies use 45/16 as a standard, which works out to 2.8125.
The 53/18 that I run on my old Peugeot works out to 2.95, which makes Suikerbossie a proper beast to climb, although the flat speed is exhilarating.
The gist is that if your gear ratio works out to between 2.5 and 3.0, you have a very rideable bicycle even with a few hills thrown in. Anything above or below that is going to have you either spinning like crazy or kakking off up hills.
