Quote:
Originally Posted by California98Civic
Thx aeohead. If it was part of the plan for the XL1, then that settles it for me. But Capriracer's point above that tires have less air flow exposure than we might assume because they are mostly in the wheel well... How significant, do you think that is?
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Well (ha ha!), Hucho cites two researchers who found that "the flow around the lower part of a wheel remains very much the same as for a free wheel, and according to A. Morelli a wheel's drag coefficient (referenced to its own exposed frontal area) remains almost constant." The effect here seems clear: smaller tire=less drag. And in yaw, which front tires typically experience ~15 degrees, the drag increases 3x, so any reduction in area would have more effect as well.
However, since we're working with production cars, there is another consideration, wheel housing volume to wheel volume ratio. As that ratio increases (as you would get fitting a narrower, lower volume tire in an existing wheel housing), drag goes up too, about ten counts for every doubling of the ratio. And lift coefficient increases 5x as fast, 50 counts for every doubling. But, it's unclear what effect a smaller volume, narrow tire that still fills the area of the wheel opening would have; Hucho doesn't cite any data on that, and while I think I have a PDF or two on that, they're on my other computer. I'll see if I can find them tomorrow.