Nitrogen-filled tires are tires inflated with pure nitrogen gas. Nitrogen is preferred for inflating aircraft and racing cars' tires, and of late, ordinary car tires, owing to its dry nature.
Tire effectiveness and durability may be significantly affected by extreme temperatures and/or the level of the surrounding air pressure. This is especially true for aircraft tires, as they fly in high altitudes, and race cars tires, which tend to generate a lot of heat owing to the high speed and immense friction.
When using ordinary air, extremely low temperature may cause the moisture inside the tires to freeze - hence reducing their internal air pressure. In air crafts, this has been shown to destabilize the plane's balance when taking off and landing. In race cars, the moisture tends to expand after exposure to the friction so much that the tires may even burst.
However, pure nitrogen is dry and resistant to the effects of extreme air pressure and temperature. As such, it is considered the ideal gas for tire inflation as it supports both balance and durability in aircraft and car racing tires.
For everyday car tires, nitrogen enhances durability, as the effects of friction are lessened, and helps retain optimal pressure levels.