On Mon, 03 Nov 2003 00:20:28 GMT, Rick wrote:

Steven Shelikoff wrote:

The wheel.

The area of the wheel exposed to the gas is so small compared to the
area of the tire producing the heat that I doubt it has much of any
practical value in dissipation of heat above and beyond air flow over
and radiation from the tire itself.

Actually, the area of the wheel exposed to the gas in a race car tire is
pretty large compared to the area of the tire since they are wide and
low profile. A narrow, high profile trailer tire doesn't have very much
wheel exposed to the gas for the amount of tire area producing heat.

Though it doesn't apply much to boat trailer tires, the heat
conductivity of the gas would work against tire cooling in the case of
race cars and aircraft since it would serve to increase the rate of tire
heating in heavy brake application. Many aircraft tire failures are due

Of course it all depends on the type of racing. During most racing like
road racing, twisty corners, etc, heavy braking is applied but for very
short durations. Superspeedway racing, not at all. There's plenty of
cooling air ducted to the brakes and the rest of the suspension
components can also act like a heat sink since they are directly
attached to the brakes and wheel. On the other hand, the tires are
always generating heat whenever the car is moving, and especially in
turns. Heat is the enemy of tire life and whatever can be done to take
away more heat from the tire will help. That being said, I sure
wouldn't want hydrogen in my tires.

to overheated brakes, heating the wheels to the point of causing the
tires to blow out or burn, not from heat generated by the tires themselves.

Slowing a 747 from 180 mph to taxi speed is hardly the same thing as
bleeding off 40 or 50 mph from a super light race car. There's a whole
different set of braking requirements, and aircraft brakes are in many
cases under engineered since they depend so much on engine braking to
slow down.

Steve