Nitrogen inflation ensures that your tyres get 99.9 per cent of refined nitrogen. Tyres with that amount of nitrogen roll more freely, because this gas is lighter than compressed air. Tyre wears more slowly when it is fed on nitrogen. Nitrogen increases tyre life by 10 to 15 per cent. Air has more moisture and it oxidises from inside eating into the rim. Nitrogen is trouble-free on that front." Although the free movement of the tyres make for fuel efficiency, we refrains from telling how much, for want of a thorough study on the subject. The nitrogen tyre inflation also thrives on the fill-it-shut-it concept and is marketed as a godsend for lazy bones — "The nitrogen will stay inside the tyres for well over three months, which means you don't worry that often about the air pressure. Thanks to thinner tubes, nitrogen might slip out of two-wheeler tyres faster."

There appears to be increasing numbers of people promoting Nitrogen as a tyre inflation media in preference to normal air.

The claimed advantages are:

• The molecules of Nitrogen are allegedly larger than oxygen thus providing a more stable inflation pressure.
• Nitrogen is more stable under temperature fluctuations hence maintaining a more consistent inflation pressure.
• Nitrogen has a lower moisture content and hence has less corrosive effect on the tyre and wheel.

Promoters use the more stable and consistent inflation pressure argument as providing better tyre mileage, better fuel consumption and better tyre casing durability.

he size of a Nitrogen molecule is very comparable with that of oxygen and as air is made up of about 80% nitrogen the effect on slow leakage will be very small.

The temperature fluctuation in tyres in everyday use is small and pressure increases or decreases have never presented a problem, providing the tyre is correctly inflated in the first instance.

Given that tyres have been designed around normal air inflation for approaching a century and Nitrogen even longer, then if there was any significant advantage, Nitrogen would be the common inflation media, which it is not.

With regard to the "less moisture" argument, tyre 'inner liners' have developed to a sophisticated level and are designed to take account of moisture in normal air. Therefore providing the tyre is not damaged air remains a safe practical inflation media. If however the tyre does become damaged and the steel reinforcement becomes exposed there is a risk of corrosion taking place. Nitrogen would have a marginal positive effect under these circumstances. However, given that nearly all damage to a tyre that could cause exposure of the steel wire, comes from external sources it is most likely that the atmosphere and not the inflation media would cause any corrosion of the steel.

There are positive arguments for the use of Nitrogen in specialist areas such as Formula 1 racing and applications where tyre temperatures are high (Aircraft) or where the risk of explosion is high (hazardous materials). In these circumstances Nitrogen offers advantages of better stability during rapid temperature changes.

In conclusion Nitrogen may offer some small advantages over air, but in everyday usage of tyres the effect would be extremely difficult to measure and any benefit marginal. Users would have the added complication, of having to return to their specialist tyre dealer to have tyre pressures adjusted, as the use of airlines at local garages would nullify any advantage that is offered by nitrogen.