[maanma]

This is how I understand this tyre wind deflector problem:

Main target is minimize (almost) horizontal wind contact angle of tyre. Default angle depens height of LOADED car and tyre diameter. Contact angle is much higher small tyre diameter combined to tall under space. Maximum and worst contact angle is vertical. This worst case scenario may not became visible under 80mph conditions, but there it still is.

To smoothen contact angle is to use triangle which hypotenuse is long downwards (as far possible) and guiding edges smoothed rounded (D -shape). Optimum angle does not overgo smooth change angle of 4 degrees (to keep wind smooth). Wind guide may be shaped to guide wind direction of need. This triangle should also go near tyre to maximize prevent wind overgo the tyre longer route.