Aero Loads and Tires

[desmo]

We've all read how aero loads at high speeds can more than double the downward
force fed into the tires compared to the static weight of the car. My questions
are: Does this increase in force manifest itself as a proportional increase in the
area of the contact patch of the tires? How does the aero downforce affect the
Coefficient of Friction of the contact patch? And finally: If one was to have access
to dynamic telemetry from a wheel tire pressure sensor, how would this change as
a car accelerated from a standstill to 350kph as enormous aero loads are fed
through the tire into the track?

[yelwoci]

Desmo,

<<Does this increase in force manifest itself as a proportional increase in the
area of the contact patch of the tires?
>>
Depends on the structural strength of the sidewall and air psi in relation to load.
Inevitably it does a bit, especially on road tyres.

<<How does the aero downforce affect the
Coefficient of Friction of the contact patch?
>>
I did a physics experiment on this when I was a kid! Given a particular compound and temperature the coeffiecient of friction doesn't change for a wide 'N' Normal load. Mind you if it gets so massive it can force the rubber into the surface structure, then you get bond tearing!
F=uN, F=Force at 90deg to N and u=Coeff Friction


<<If one was to have access to dynamic telemetry from a wheel tire pressure sensor, how would this change ....
>>
Within reasonable loads and without structral failure it doesn't. (though if the tyre warms up it will!)

IanC

[Dino IV]

Aerodynamic forces grow to really amazing loads.
If I remember correctly, wasn't there a Group C Silk Cut Jaguar in the early nineties fitted with such an enormous rear wing that the rear tires exploded?

[ma]

I'm not positive about Group C aero loads, but the old GTP cars could get over 14000 lbs of downforce at speed.