the bigger the ratio (bigger ring/smaller cog) the harder the gear and theoretically faster bike. Your gear can get you to a car's speed without spinning insanely fast but in reality getting that gear up to speed is gonna be hard as hell. Also, someone that can spin a lower gear really well will probably be faster than the guy trying to pedal a tall gear at a low cadence.
Originally Posted by
Haagenize
i used to run 46x16 which was fun, but then i switched to 46x19 for winter gearing, and i loved it
That's what I run now and it really isn't hard to go around 20mph, which I think most people with good fitness will be trying to ride at. But I get that others will want to stick around 70 gear inches or just over.