ryoung

Nitrogen is strongly recommended for racing where tires often run 200 oF or hotter.

The problem with air is that it's normally not just air. More often than not, the "air" in your tires contains liquid water from the air compressor and/or the lubricant used on the bead when the tire was mounted on the wheel. Normally the air (or nitrogen) pressure in a tire increases predictably about 1 psi for every 10 oF of temp. If there's liquid water in the tire (and water is usually present if you're filling the tires with "air"), pressures sky-rocket unpredictably as the water turns to steam.

On the street, there little benefit from using nitrogen; the tires normally don't run hot enough to cause a problem. On track at Mid-Ohio however, the left-front tire on my S8 has hit 240 oF. With a starting cold pressure of 36 psi, I normally expect a 47 psi hot pressure. My tires were filled with (wet) air however, and that LF tire was almost 60 psi. When I let "air" out, I was burned by the steam.