Wow. Cool article. On a different point, the authors also make this surprising claim:
Quote:
"As it has been previously investigated when the wheel starts to
rotate there is an expansion in the tire due to inertia [6]. This
expansion changes the tire shape, see Figure 6, and affects the
rolling resistance. The tire radius may change by as much as
8mm, depending on the material properties, weight of the
vehicle and speed. For the set-up used during the test the
maximum tire expansion measured was 2.5 mm for the
velocity of 200 km/hour."
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8 mm would be a quarter inch and 2.5 a tenth of an inch. Not insignificant, though not huge, either.
EDIT: Back to the main point of this discussion for a second, it seems figure 13 is the most important in the article as it takes into account both ventilation drag and aerodynamic drag for a calculated total figure. Here's that graph:
2CD EDIT: (don't hate me for all these edits, lol)... rim configurations.
ARTICLE AUTHOR'S PREFERED CITATION:
Vdovin, A., Bonitz, S., Landström, C. et al (2013)
Investigation of Wheel Ventilation-Drag using a Modular Wheel Design Concept
SAE International Journal of Passenger Cars - Mechanical Systems, 6(1): 308-315.