I want to offer this study into the mix. Ventilation drag seems to be a closely-related issue.
Alexey Vdovin, "Investigation of Aerodynamic Resistance of Rotating Wheels on Passenger Cars," (Gothenburg, Sweden: Department of Applied Mechanics, CHALMERS UNIVERSITY OF TECHNOLOGY, 2013).
http://publications.lib.chalmers.se/...302/176302.pdf
See also:
http://publications.lib.chalmers.se/...ext/133661.pdf
"Blocking the crossflow through the rims result in increased static pressure in the front wheel house and thereby an increase in lift, whereas blocking the crossflow in the rear result in increased downforce due to an increased flow rate through the diffuser. It was however shown that the resulting flow around the rear wheel was highly dependent of the rim design in the front."