Roflcopter-rex
#9
Actually there is a point to using nitrogen in the tires vs. the regular air we breath. Bigger molecules. It doesn't leach out through the rubber as quickly. Doesn't expand as much when hot either. 6ul's have 2 valves in them just for the purpose of using nitrogen.
A better analogy would be the shysters that say you can inject water into your cars fuel/air system. Oh wait, that works too....
#15
Air is mostly nitrogen anyway. But yeah, it doesn't leak out quite as bad, because you don't have the other ~20% or whatever of oxygen, carbon dioxide, etc.
The primary benefit is that it is a dry gas. It will expand/contract the same as any other dry gas (see the Ideal Gas Law), but this will be significantly more predictable and controlled than tires filled out of a compressor that will have some component of water/oil/whatever mixed in.
FWIW, in either ALMS or Grand Am they were simply filling the tires with dry air. Some teams drained them and filled them with nitrogen to remove the remaining ~1% moisture that you can't get out otherwise, but for many, so long as the air is dry, it's good to go, as pressure change with temperature will be predictable.