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Trailer Tires Overheating.
On Wed, 05 Nov 2003 06:25:44 GMT, (Steven Shelikoff)
wrote:
As a quick and dirty example, Nascar wheels are 15" dia x 9.5" wide.
The tires are 27.5" dia with a width of not more then 13.2". To make
things easier, assume flat sidewalls, which will make the area
calculation below come out on the low side. The sidewall area is around
2*(27.5-15)*pi = 78 sq in. Also ssume the wheel is a cylinder, which
will also make the area calculation come out on the low side so it sorta
cancels out. Also, assume that the bead takes up around 1/2" of the
wheel width on each side even though it's a little less, so the area
calculation of the wheel area will be a bit low. So the surface area of
the metal inside the tire is around 15*8.5*pi = 400 sq in, or about 5
times the sidewall area.
Holy cow, major brain fart. It's too late for deep thought. The area
of the sidewalls is 2*((13.75*13.75) - (7.5*7.5))*pi = 834 sq in. So
that's around twice the wheel surface area. However, those tires work
out to be a profile of around 50. Other types of racing, like F1, have
much lower profile tires so they have a much greater wheel area vs.
sidewall area.
In terms of profile, if you have a profile of 50 you'll have twice the
sidewall area as wheel area. A profile of 33 will give you about the
same sidewall area as wheel area inside the tire.
The funny thing is, that's the way I thought about it first but when the
math didn't work out, I didn't post it. The reason the math didn't work
out is that I was using the formula for circumference of a circle
instead of area of a circle to figure the sidewall area. Sheesh!
Steve
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