> >That's what they told me at the dealership too. I asked "larger than what? Air is a mixture that's already 78% nitrogen." Didn't get an answer. > No idea ab

> >That's what they told me at the dealership too. I asked "larger than what? Air is a mixture that's already 78% nitrogen." Didn't get an answer. > No idea about molecule size, but the reason for nitrogen is that it expands less than air when heated, so tire pressure doesn't change as much when driving hard on a track. Pressure/temperature/volume for any gas are governed by the ideal gas law, which doesn't care what your molecules are. (Sure, it's an approximation, but certainly one that's imperceptibly reliable enough for car tyres).