[mikeyjd]

Originally Posted by California98Civic

That's interesting, of course. The article speculates on the same theme. But .28 is still lower than the C&D tunnel offers (.30). So, I'm still wondering if the testing method makes its own noise. Did Mercedes test without the wheels spinning? That kinda thing.

Originally Posted by aerohead

One SAE Paper from General Motors in the 1960s reported that the difference in Cd between spinning and stationary wheels was of such a low statistical significance that it didn't warrant the time and expense to test; and spinning tire effects could be easily simulated with trip strips in the tire/wheel area.
Exposed-wheel race cars MUST be tested with spinning wheels.