Answer: "Airflow Around a Wheel: Why Do Hub Caps Bulge Out?

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seanclery
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Hi all,

Just Wondering quickly, do the static hub caps on a Formula one car(say Brawn GP) bulge out slightly or are the flat and flush with the wheel?

If they do bulge out, why does this produce less drag?

Thanks

Sean
 
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First to be sure we are on the same page, your talking about the half-caps right? Only cover the top half of the wheel? I took a look at a picture and it appears that they do bulge out slightly. They could reduce drag by not allowing the air that is moving around the tire and off the trailing edge of the front wing to collect in the recess of the wheel. The spinning spokes would cause turbulence, increasing drag. Smoothing out the airflow over that area reduces drag. They are only necessary on the top half because the wings trailing edge sits about halfway up the height of the wheel. Similar thinking to a stock bodied drag car with the spoiler coming straight off the rear end. It's purpose is not to create downforce, but simply to smooth the airflow, reducing drag. A secondary purpose could be to scavange air from the bottom half and trap it or pull it inwards for brake cooling. This is all thinking out loud, I am not an aerodynamics guru.

Chris
 
You may not be a guru (who really is though?) but you've got it spot on. They should be banned though, simply for being ugly. Technically they are brake cooling aids, with a 'not-so-secret' aero improvement.