Nitrogen in Tyres and Road Safety
Introduction to Nitrogen
The air we breathe is 78 per cent nitrogen and 21 per cent oxygen. Nitrogen gas is non-combustible, non-flammable, non-corrosive in pure form and environmentally friendly. Nitrogen tyre gas does not attack or oxidise the rubber of the tyre from the inside like air does. It is a pure gas, so it does not hold heat and the tyres run cooler.
Nitrogen inflation of tyres has been common for tyres fitted on race cars such as F1, as well as aircraft, trucks and vehicles used in mining and other industrial applications for a long time. Nitrogen gas is also used in Tour de France bike tyres, in all the space shuttle tyres and even the moon buggy had nitrogen in its tyres.
Planes fly at heights where temperatures may be as low as -40C. Any moisture in the tyres can freeze causing vibration and balance problems when landing. Pure nitrogen is dry so eliminates this problem (as would dried compressed air).
In motor sport the smallest fraction of a second can make the difference between winning and losing. Filling with nitrogen can reduce tyre pressure variation caused by changes in tyre temperature. It is also the biggest molecule gas, so it is the slowest gas to migrate through a tyre, and there is therefore very little loss of pressure.
Benefits of Nitrogen in Tyres
Are there other benefits apart from the cool fluorescent green valve stem caps on tyres filled with Nitrogen?
The experts say that there are many very compelling benefits to be enjoyed from the practice of filling your vehicle’s tyres with nitrogen.
These benefits include:
- The key benefits are a slower rate of pressure loss and cooler running temperature of tyres.
- The molecular structure of nitrogen differs from that of air, in such a way that it escapes through the tyre’s inner liner or tube at a slower rate than regular compressed air.
- The result is a dramatically slower rate of pressure loss in a tyre filled with nitrogen. For example, it might take up to six months to lose 0.14kpa with nitrogen, compared to just one month with compressed air.
- Tyres inflated with nitrogen also run cooler than those inflated with air, with some significant advantages.
- One such advantage is an improvement in tyre life of up to 20%, because by reducing the tyre’s running temperature, you can increase its tread life.
- Improved road handling is another benefit that stems from cooler running tyres.
- As tyres heat up, their inflation pressure increases, which then reduces the size of the tyre’s footprint - the area that has contact with the road - the tyre then loses grip because of this smaller footprint. So the cooler they run the better the tyres will grip the road.
- Nitrogen should lead to reduced corrosion - because unlike air there's no moisture in pure nitrogen
Nitrogen and Safety
It is important that we look at the benefits of Nitrogen gas from a road safety perspective:
The facts are clear and there is evidence to suggest that nitrogen tyre inflation is preferable to air inflation. There are compelling facts pointing towards better road handling and improved tyre life of up to 20%...
The top three reasons for blow-outs are poor condition, overloading and under -inflation. Poor condition comes from drivers not being responsible and running their tyres too far. Overloading comes from the same irresponsibility and the law not being enforced as it should be on both counts. We can however do something about under-inflation. The answer might be to fill tyres with nitrogen tyre gas.
Why do we say so?
- Compressed air contains water vapour, which accelerates rust, corrosion and damage to wheels, resulting in leaks and loss of pressure.
- Water vapour absorbs and holds heat, and when it changes from liquid to vapour, the water expands in volume. So tyres inflated with wet air tend to run hotter and the pressure fluctuates more. Nitrogen has very little water vapour.
- The Goodyear Tyre and Rubber Company in the USA stated in a bulletin that it supports the use of nitrogen as an inflation gas in all Goodyear products and that the use of nitrogen will not affect its tyre warranties.
- Michelin USA also issued a bulletin and mentioned that it supports the use of nitrogen, based on its ability to better retain pressure over a long period of time.
As with normally-inflated tyres, it is advisable to check tyre pressure regularly to prevent excessive wear. Regular tyre pressure test intervals should still be maintained, as the tyres on the drive axle of the vehicle tend to lose pressure faster that the non-drive wheel axle.
Availability & Affordability
The practice of filling ordinary passenger vehicle tyres with nitrogen was not common in South Africa until recently, primarily because it was too expensive. Today, machines such as those at Tiger Wheel & Tyre stores generate and store sufficient volumes of nitrogen to make it cost effective to inflate the tyres of ordinary vehicles with nitrogen.
Changing to nitrogen involves removing all the air which is already in the tyres and then re-inflating them with purified compressed nitrogen. There will be a one-off charge per tyre but once filled with nitrogen any future top-ups would also have to be with nitrogen if any advantages are to be maintained.
Nitrogen inflation is available at a nominal cost, at all Tiger Wheel & Tyre stores countrywide and top-ups are free thereafter. Nitrogen is the ultimate tyre inflation gas and it is now easily available in South Africa - from about 120 tyre dealers all over the country.
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