Annoyingly located in the far corner of many tv tennis courts (right where it very often ends up out of frame or behind the chair umpire when watching on tv) is a display that shows the speed of the most recent serve in either mph or kph, depending on the tournament.
In some tournaments, the number disappears after a few seconds; in others, it stays up throughout the rally and only disappears right before the next serve; and in yet others, it doesn’t disappear at all, just gets replaced by the value from the next serve or between games/sets. Wimbledon falls in the last of these categories.
In most tournaments, at least as far as I’ve noticed, the speed is clocked and noted for all serves, regardless of where it ends up.
At Wimbledon, however, I’ve noticed that if a serve is judged to be a let, the previous speed disappears, but no new measurement is added.
If the serve is successful, the speed is shown, of course. Even if it’s a fault, the speed is shown – whether the fault is that it’s long/wide or that it hits the net and doesn’t go over. The speed is even shown if the ball hits the net, continues, but lands outside the service court. But if the ball hits the net and continues, landing inside the service court, no speed is shown.
Why is this? What’s so special about lets that their speeds should be withheld from statistics-crazed viewers like me when the speed of both successful and unsuccessful serves are given?