Originally Posted by wphamilton

Sorry but I disagree! The reason is, the shape and texture can matter as much as the reference size, and additionally what the air is doing at that point. Is it attached to the surface in a smooth flow, a momentary separation and reattachment, turbulent, low pressure? What about parasitic drag? And then we have real world considerations such as what happens when the wind shifts even a few degrees. It can become complicated very quickly and the situation we see on a bicycle is more dynamic than we'd think at first grasp.