How do you estimate the speed of Tour de France riders on tv? I was watching Tour de France with my father (who is a cat 3 racer), and he claimed to be able to estimate how fast the riders were going by observing the cyclist on the screen. I didn't believe him at first, but as we watched, and the screen showed their speeds, he was fairly accurate. How is this done?
This is not that hard for someone with a lot of riding experience. Often times you can tell the gear a rider is in from the TV. Then you can see the rider's cadence, and the road grade is often given. So it's fairly easy to guess the speed to +-2 mph. Plus, on a mostly flat road, the peleton will be riding at somewhere between 24-27mph, unless they are trying to chase down the lead group. If the lead group is gaining on the peleton, you know they are riding somewhere north of 24-27. And the opposite would be true. At the end of the sprint, the lead riders will be somewhere between 30-35. Given all this, it's not hard to fairly accurately guess the pace of any individual rider, at any given time.