Air flow over automotive brakes 2

[frankiee]

With road wheels that have a unidirectional vent pattern built into them, do the louvers draw air from the outside to the inside drawing cooling air over the brakes or
- does it draw hot air from the brake area out to the air outside?

 

[EdStainless]

In theory air will flow from the hub, through the rotor, and hot air will exit the OD.
In practice, anything that improves surface area and turbulance is a help. The actual pattern/flow aren't a big deal.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[JimCasey]

Ed is right that ventilated rotors act as compressor impellers, using centrifugal force to draw air throught the internal cooling passages.

Usually the cooling air that has passed throught the brake rotors exhausts through the wheel and to the outside. That is why so many cars have black brake-dust contaminated front wheels.

Theoretically wheels with directional spoke/rotors would draw air from under the car, both cooling he brakes and improving downforce and thus roadholding. But at 60 mph the typical tire is turning less than 1000 rpm, so the fan blades are turning more slowly than a typical electric fan and the greatest advantage is in impressing one's peers with cool-looking equipment.