Originally Posted by usual_suspect

There are several theoretical advantages to using nitrogen in tires:

- contains less moisture, so pressures stay more constant with heat cycles (that's why racers user it)
- completely inert gas, so less corrosion of wheels and oxidization of rubber (that's why truck fleets use it)
- less pressure loss since larger nitrogen molecules don't migrate through the rubber as easily as oxygen molecules (questionable, IMO)

You'll hear stuff like "lighter/heavier", "better handling" or "fire resistant" mentioned, but these are just stupid.

In actual practice, street cars don't heat tires up enough, or keep tires long enough to get any real benefit. On the other hand, it won't do any harm either.

Originally Posted by txgcoupe

But remember, water vapor will constitute less than 1% of the air in the tire.