In the late 1940s and early 50s, when I was racing, and riding with the Franklin BC in Columbus, Ohio, my fellow racers and I had an agreement. On our Sunday rides we'd ride 66" gearing for our impromptu sprints. I cheated a little and rode a 42 x 16 (69"). That was my training ratio. When I raced on the track, I switched to a 52- tooth chain ring (85") and won a lot. With the same maximum RPMs. Over time I learned to shift up and down to maintain my optimum RPMs whatever the terrain. And won road races. I'm still most comfortable with the 69". Although I do spin out some and have to back off to stop 'barrassing butt bounce.
Mark Fulton Going out for a 69" spin this afternoon in Redwood City California USA