Im fortunate (or unfortunate) depending on what the problem or question is at the time to have some close contacts with a varied group of motorsport competitors. One such incident was with a well known truck racer ( large like Kenworth-DAF-Volvo etc ) with water spray to the front rotors, the spray nozzles had residual check valves in the lines to prevent water loss when not in operation- unfortunately on this occasion the valve must have had a small piece of debris in it and the nozzle had slow dribble when not in use. at the completion of the meeting after the final race the truck was left standing in the pits, a few minutes later there was a huge 'bang' like a shotgun being fired & everyone ducked for cover thinking a tyre had exploded. No one had a clue what had 'exploded' & it was not until they tried to move the truck that the reason was discovered, the culprit being the leaking nozzle on only one portion of the red hot brake rotor which had split in a radial direction.
The centrifugal fans on each wheel arrived down under on the Aussie Touring cars fairly quickly- I remember reading an article on Greenwoods Vette and noting the same setup on cars at Bathurst that season. I also note that many Auto Manufacturers incorporate a fan design into the alloy wheel centers and blurb on about brake cooling, then fit the same wheel to both sides so that air is being moved into the wheel arch on one side & extracted out on the other
Sorry Fran , slow typist- When you consider that the wheels are only ever going to turn at around 2000 rpm max it takes a fairly efficient centrifugal fan design with a large exit OD to be of any use.
Jac Mac