"Mark Browne" wrote in message
news:8H_mb.39146


The reason is that the water in the
air does NOT act like an ideal gas.

Gosh, I didn't realize that there had been a change in the laws of physics
since I went to college! When did this happen?

Man, things were easier back in my day when any gas obeyed the gas laws!
Remember when the steam tables were what you would use for any gas you
didn't know the properties of?

Think about what happens to the
pressure/volume curves as the tire reaches 100 degrees C.


The vapor pressure for water will vary over a very large temperature range.
Fortunately, it is predicatable and monotonic. If you didn't have liquid
water in the tires when they were cold, you won't have any liquid in them as
they heat up.

I can see reasons that a race car might want to use nitrogen in their tires.
It is a nice, safe gas. It is realatively cheap. The fact that it is
readily available in a very dry state can have its advantages: I can imagin
that avoiding any condesation when the tire was cold could be an issue,
especially during the winter. The issue would be maintaining a
"predictable" inflation pressure as the tires went from "colder than when
they were inflated" to nominal operating temperatures. I suppose that
condensation could also be an issue when the wheels were balanced.

Rod