Antique Bicycle : 19 Steps (with Pictures) - .
The gear inch is exactly the size of the front wheel; that's where the gear inch standard came from. So this bike will be about a 50-inch gear (after you add the tire thickness to the 48" rim). I always wondered why the gear-inch number left out the pi factor that would tell you how many inches you'd travel in one pedal revolution, i.e. [pi*diameter*chain gain] vs the [diameter*chain gain ...