OK, so the reason nitrogen is used in aircraft tires is because at the -50 deg. Celsius temperatures the tires cool down to when cruising at 30,000 feet altitude, the humidity in the air in the tires turns into frost, and that significantly lowers the tire pressure. When the plane comes in to land, the tires are still extremely cold and therefore at a lower pressure than they should be at to support the weight of the airplane on landing. Using pure nitrogen avoids that problem because no precipitation of frost occurs.

Is that the truth, the whole truth and nothing but the truth?

I still think using helium would be more fun. We could inflate plastic bags with helium from our car tires and suck the helium out of the bags so we could talk like Micky Mouse for a few seconds. That's gotta be worth a laugh if you're in court or meeting you're kid's school teacher for the first time.