Race car teams have long used nitrogen to inflate tires. Compressed nitrogen has virtually all of the moisture removed. Very few air compressors have this capability, one of the exceptions being those that are used to refill SCBA and SCUBA tanks. The reason for using nitrogen in race car tires is the desire for constant and predicatble tire pressures when the tire heats up. Moisture in a tire inflated with air vaporizes and expands, causing the pressure inside the tire to increase. Even small changes in tire pressure can noticeably affect the handling of the car. By using nitrogen instead of air, teams have more control over how much the pressure will increase when the tires heat up.
For the rest of us there are benefits to using nitrogen. Compressed air contains 80% nitrogen, 19% oxygen, trace amounts of other gases, and water vapor Over time, the pressurized air inside a tire migrates through the tire. The oxygen and moisture in the air react with the rubber compounds in the tire, causing them to break down and lose strength and durability.
Unlike nitrogen which is an inert gas (does not readily react with other chemicals), oxygen is affected by changes in temperature, which affects the rate of air loss from a tire. Oxygen contributes to the aging of the rubber, while nitrogen does not. Because nitrogen molecules are slightly larger and less permeable than oxygen and other gases in air, it migrates considerably slower through a tire. On average about three times as long.
