By inflating tyres with nitrogen, and not air, which contains oxygen, the perishing process is slowed. So nitrogen obtained from dried air is used and the working life of tyres can be more than doubled by this means. The use of nitrogen for inflation is not exclusive to truck tyres. Some trains on the Paris Metro have rubber tyres, and these are also inflated with nitrogen. John Moores University Liverpool a. Oxygen in the air of normal tyres slowly leaks out through the rubber walls, and the resulting underinflation leads to higher tyre wear with a consequent decrease in safety and higher fuel costs.
Nitrogen leaks out much more slowly and keeps the tyre inflated to the correct pressure for longer.
This reduces maintenance costs and, more importantly, also improves safety. Because it is inert, nitrogen also reduces the degradation of the rubber that frequently occurs in the presence of moist oxygen. Nitrogen has been increasingly used where there is a lot of wear, or where performance and safety are key issues, such as in heavy-duty trucks, Formula 1 and Indycar motor racing, military and civil aircraft, and also in the space shuttle. In the cases of racing cars, aircraft and the space shuttle, the reduced risk of tyre fires is seen as an added advantage.