and that ten degrees can come from a hot road surface or just running the tires. Tires running on the summer freeway at 80 mph might gain 2 or 3 pounds of pressure. So if the tires read 34 pounds at 70 degrees it would take something like a 200 degree rise in temps to push the tire to its maximum unsafe pressure. It's not really a big concern to most of us. Unless you like tires with 50 PSI in them in the first place.
Nitrogen? That's for the big boys. If you race, and manage to keep a set of tires more than one race, it might be cost effective. It is more stable than Air and doesn't expand as much. Great for your super fuel dragsters, or your Indy cars but not much else.
Yes, the molecules are larger than most other gases, but Air itself is 78% Nitrogen so comparing it to oxygen is silly because we fill our tires with compressed air. The most pressure you could lose through the rubber is 22%, so maybe 8 PSI. And face it, oxygen is explosive. Not a good choice for tires!
Sun and oxygen are the two biggest enemies of tires. But oxygen is in the air around us. Filling the tires with nitrogen doesn't make any real difference in the life of a tire. Unless you just like telling people you fill your tires with nitrogen it really makes no sense. Even a super car can't be run at 200 mph for hours on end in any country in the world. Except maybe the interior of Australia? But considering the roads there it would be suicide.
I've heard of those ritzy tire monitors going bad and showing either 3 PSI or 60 PSI in tires that are fine. And having each tire coded to a certain corner of the car makes the recommended tire rotation a royal pain. If you could just push a button and change the programming that would be fine but most of the time you can't, it's a dealer reprogramming. I'd rather have a digital gauge in my glove box. When that fails it only costs a few bucks to replace.
![[linked image]](http://farm4.static.flickr.com/3021/3077577396_2bfd2a71af_m.jpg)
Illegitimi non carborundum
In memory of Denis Keegan.
