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Keep it cool

2007-05-04 14:34

Colin Mileman

Ever since the pneumatic tyre was invented way back in 1846 by a certain Scotsman, Robert William Thomson, tyres have been filled with air - exactly what you and I breath.

But in the last couple of years, nitrogen has been purported to offer a better alternative for a variety of reasons - and yes, these claims are well founded and fully justified.

And it's not an unproven claim, as nitrogen has been used for years with good reason for a variety of extreme applications, including commercial and aircraft tyres, as well as in the top forms of motor racing, such as F1, IndyCar and Nascar.

Nitrogen is actually far more prolific than we may think as it comprises 78% of what we breath, with 21% being oxygen.

According to the experts, the life of a tyre is adversely affected by two elements - oxygen and moisture, both of which are present in the atmosphere. As an inert gas, nitrogen is apparently non-corrosive, non-flammable and non-combustible, and is capable of prolonging the life of a tyre compared to using normal air.

The fundis suggest that the difference between the pressure of air in a tyre, and the pressure outside, causes oxygen to slowly permeate through the rubber, leading to gradual deflation of the tyre - which obviously results in under-inflation and increased wear.

The indication is that by creating the same concentration of oxygen inside and outside the tyre, the correct pressure is maintained, leading to optimum operating conditions for the tyre, and the best possible durability.

This does not, however, suggest that it eliminates the need to check your tyre pressures on a regular basis. Regular tyre checks should still be carried out - not least of which to check for tyre damage, punctures or leaks.

Naturally, this also has direct benefits in terms of fuel efficiency, as an under-inflated tyre produces more rolling resistance and requires more fuel to maintain the same comparable speed - which simply means your car's fuel consumption goes up, it costs you more and it impacts on the environment.

There are other benefits too, as nitrogen isn't subject to the same heat and expansion characteristics as air. With oxygen, the tyre pressure can increase by as much as 20% from a cold start to normal driving conditions.

By comparison, nitrogen experiences a minimal increase in temperature or expansion, and provides for cooler running (between 10% - 15%lower), more consistent performance characteristics under all driving conditions and, once again, improved tyre life.

Regardless of what you choose to fill your tyres with, it's important to check pressures when the tyre is cold, as it's the only reliable method for ensuring the correct pressure and ideal performance. And use the same pressures as recommended by the vehicle manufacturer

The most attractive part, if you listen to the best industry advice, is that nitrogen is the way to go as it can extend tyre life by as much as 20 to 30%, which is a significant improvement - whether you drive a budget-beater, an executive sedan or operate a large trucking fleet.

Most of the large tyre retailers offer the option of filling up with nitrogen - either when you purchase new tyres or simply if you pop in to make the change. And although there may be a minimal charge (around R15 per tyre, usually with free top-ups thereafter) it's well worth the effort and the investment, as it will save you a whole lot more in the long run!

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