Originally Posted by
DrIsotope
See, we have this thing here where the elevation changes— sometimes a lot. The local pro races (aside from the crit) average 23-25mph. Pros. There are a couple of local Strava segments that hold 26-27mph for a few miles— but whole activities? Nope. I rode a 20mph tailwind all the way to the Pacific Ocean, almost 70 miles, and averaged 23.7mph. Open roads and hills.
The average speed at local races is not the ultimate, because tactical considerations often temper the speed. That same group of cyclists could go faster if their goal was to work together to maintain the highest possible speed. You may not have seen one, but sub 4-hr centuries are not that unusual. (I know at least a dozen riders that have done it.)