Originally posted by Cryder
I raced pro-am in Europe for a while, so I'll bite on this one.
First, understand that there is no "average race" - each one is entirely different course to course and race to race, but there are speed benchmarks that you will only see in a pro peleton. Second, the expected speed depends on the time of year and what type of race it is in what conditions. The easiest way to answer your question is to check each races average time vs. the distance.
In regular season racing, a normal Belgian kermese was in the high 20's and sometimes low thirties for an average. For a larger pro/am semi-classic, if you were in a break early it almost always meant a 30+mph day on a relatively flat or rolling course. Stage races tend to have slightly slower averages then the one day classics because of the extended tactical nature of the race.
Also, its not that the pace stays at a constant, its the accelerations and decelerations that are averaged over the course. If the race hits a hard spot, the speed may jump up to the mid to upper 30's for an extended attack, and then settle back down to the mid to high 20's.
Its really much easier to understand how fast the pace is by considering how "hard" the race is. An average category 1 racer in the US will feel like a Cat4 racing against Cat1's on European turf - its that freakin hard. Race with the pros and the process starts over again. A seasoned European amatuer will likely suffer mightly in his first two or three seasons out with the big dogs. I believe that Lance's first pro race was so brutal he almost left the sport. There is a huge amount of adjustment time that a rider has to go through to ride at that level. It really does take years, becuase no matter what the hammer is always down.
Hope that helps...
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