Quote:
Originally Posted by Old Tele man
I'm more inclined to think the "differences" could be the result of 'static' (no tires rotation) versus 'dynamic' (dynamometer) wind tunnel testing techiques. Spinning wheels create eddy currents which create a LOT of drag!
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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.