Why do riders in various realms of cycling call out their chain rings in front and rear as xx/yy and xx/yy but then say, they "should probably ride xx?" and indicate a one or two number difference in the front or the rear?? I mean honestly, SO many people talk about a one or two tooth difference?? Are that many people SO totally finely tuned that they command the maximum tolerances +/- a tooth?

Just curious.

Thanks.

Erik.