Heresy! Smooth Wheel Covers- Myth Busted!!!

[freebeard]

Appears benign, but it makes me nervous when a link drops a file in my system rather than opening in the browser

[aerohead]

Originally Posted by Phase

https://core.ac.uk/download/pdf/211225703.pdf

seems like fully closed wheels increase the base pressure at the rear of the car. they also prevent air from coming out of the rims and feeding into the jetting vortex behind the wheel

Any turbulence created along the body robs from the total available streamline energy, turning it into heat. This lost energy can never be converted back into useful pressure, capable of reducing pressure drag.
So anything done, anywhere on the body to reduce separation and it's attendant turbulence or vortices is money in the bank.