I was thinking about this after I read it and when you consider what's really happening to the Wheel/Air relationship, it sort of boggles the mind. Here's what I mean.
When the wheel & tire are rolling along under the car and
Through the air (which is stationary), to the air, the tire comes to a dead stop when it is on the ground and the tire surface is going twice as fast as the car when the tire is at the top of its rotation as the wheel spins on its axle. So it is a tremendously dynamic system that exists here.
This is known as a cycloid if you want to Google it. there is a lot of history behind it and a ton of math.
At first glance, you’d think the wheel is just spinning like a fan and presume what the air is doing based on that, but it is Rolling through the air which (on a calm day) is just wanting to remain in one place.
Considering this, the “blades” that may be on a wheel are doing nothing when they are at the bottom, but, on top the blades are moving quite fast, so it would seem that they are moving most of the air around the top half of the wheel and not so much in the bottom half.
Kind of a cool thought puzzle when you really consider everything going on. Way more to it than you would consider at first glance.
It is also another reminder that we need to be mindful of the fact that our cars are moving through the still air, the air is not “Blowing” around our cars. With a boat it is pretty intuitive that the water just sits there and the boat move through it, but for cars, we all seem to think that the car is just sitting there and the air is blowing over it, like in a wind tunnel. But it doesn't and a rolling tire/wheel system really illustrates the point that it is way more complicated than you would think.
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