Originally Posted by
rufvelo
The qualifying speeds for say Olympic selection works out to 23-25mph solo. So a century at around 4hrs is expected. In the pro peleton 23-28mph is the norm. On really fast decents 50-60mph is possible on closed roads where you can use the entire road but you're not pedalling at this speed, just getting a few pedal strokes in around the bends. On your own with anticipated traffic, you'll find it very hard to decend on most roads around the world at over 30mph and still be safe.
At some point it is fitness, it is form plus a racing training program to get to speed. Then there is genetics to consider - most folks regardless of training and experience won't handle 20-22mph for 4-6hrs.
With what kind of ascent, descent and wind conditions would these athletes be working at these paces and delivering centuries in these times? Averages are pretty meaningless without intimate knowledge of the conditions underwhich they are formed.