Nitrogen vs. air for tires
I have seen dry nitrogen being recommended for inflating automobile tires instead of air. Reasons given are:
1. Air's 21% oxygen deteriorates the tire, while nitrogen is inert. I can accept this, since I believe that oxygen under pressure and at elevated temperatures accelerates oxidation.
2. Oxygen in air plus moisture in air cause corrosion of metallic parts of the wheel. This, too, seems reasonable.
3. Nitrogen does not penetrate the tire walls as readily as oxygen and so maintains proper pressure longer. This I do not understand. The molecular weight of nitrogen is 28 and that of oxygen 32. Is the size of the nitrogen molecule *larger* than that of oxygen? It must be so, since the two gases are separable by the use of a semipermeable membrane. But it just doesn't seem logical to me.
4. Nitrogen-filled tires run cooler than air-filled tires. How can this be? Is nitrogen a better "thermal conductor" than oxygen, thus permitting heat from flexure of the tire's sidewalls to be conducted to the metal hub and dissipated by outside air?
If these are not an appropriate questions for this forum, would you kindly direct me to a more suitable one?