>Don, water vapor *is* steam, or vise versa.

"Steam" is ambiguous. Most people think of steam as the visible water
particles (liquid) which condense out when pure steam comes out of a
tea kettle. But yes, the relative humidity in the air is steam (or
water vapor), as is the water in a tire.

> From racelinecentral.com (note this is for racing, not our kind of
> driving:
>
>>Tire Temperature synopsis:
>>
>>Optimal temp range is between 190-240 degrees.
>The boiling point of water at 13 psig is 246F -- slightly above
>optimal range

What type of race vehicle runs at 13 psi, except those swamp things,
where heat isn't an issue?

 From your source (racelinecentral.com):

>NASCAR Winston Cup TRUE TIRE HISTORY...The tires are inflated around
>50 psi.