Tyre pressures are critical as the footprint of a tyre is the only contact a vehicle has with the road. The only control you have is dependent on that footprint operating the way it was designed to which means, at the correct pressure.
Most people are well aware of the fact you are supposed to check tyre pressures regularly but how many of us actually do? You’d be surprised at some of the results road checks uncover.
Sussex Police force, in the United Kingdom, carried out a roadside survey to check tyre pressures due to their concern with incorrectly inflated tyres. The check allowed a +/- 5psi tolerance against recommended handbook pressures.
The results of the survey were that 73% of all cars checked had incorrect pressures
Police also check the tyre pressures of every car involved in a road traffic accident in the UK. This data shows that 86% of vehicles involved in road traffic accidents have incorrect tyre pressures.
Furthermore, tyres that are under-inflated by just 20% (4-6 psi) on average can lead to your tyre lasting 26% less than it would if correctly inflated. According to police figures, 73% of tyres checked were 5 psi out against handbook pressures.
It is estimated that under-inflation of 20% can cause fuel costs to rise by 5%.
The simple answer, therefore, is that Nitrogen inflation can save you Money and keep you safer on the road.
Why do all tyres lose pressure?
Compressed air contains Oxygen and Nitrogen in roughly a 20% to 80% mix. It does, however, contain other gases as well as Water, Water vapour and dirt/ grease,
Certain components namely Oxygen, water vapour and free water that is found in compressed air are prone to permeation through the tyre structure. This is not from faulty valves or leaky rims but a natural pressure loss across the tyre and into the atmosphere. The wall of a tyre may seem solid but it is, in fact, a “Permeable Membrane” meaning gases can pass freely through it. Tyre Manufacturers coat the inside of a tyre with a Butyl liner to slow pressure loss but it is not a cure.
Of these components in compressed air, both water vapour and free water can enter the tyre in varying amounts even if identical tyres are inflated with the same gauge on the same day.
Compressed air is not a specified gas and as such will always contain varying amounts of these components that are not suitable for tyre inflation.
The Difference between Nitrogen and Compressed Air
An onsite generation system for tyre inflation carries out in milliseconds what happens in every tyre over a period of months. By filtering out the ‘active oxygen’ and water/ water vapour the product remaining provides the tyre with a stable inflation mixture that has no desire to permeate (leak) out through the tyre’s structure.
You may read about molecule size being a key factor in why Nitrogen remains in a tyre cavity. This is just plain wrong! The reasoning is to do with fairly complex physics and chemistry where there are “fast” gases and “slow” gases which are more or less prone to permeation. You can find out more about the physics behind Nitrogen Tyre Inflation in our Knowledge base including the history of nitrogen tyre inflation.
How the Nitrogen Generation Systems Works
Nitrogen is not made but harvested. Everything that is needed to make Nitrogen is already in the atmosphere around us. All the Nitrogen equipment does is separate out the ideal gases for tyre inflation and releases the ones that aren’t, back into the atmosphere. This is normally done in 2 main ways
The Membrane; Hollow Fibre Membranes, which use proprietary technology and the principles of permeation to provide a guaranteed reliable supply of nitrogen gas. Compressed air enters the membrane core and passes through the bundles of hollow fibre. The faster gases (water, carbon dioxide, oxygen and argon) permeate through the walls of the fibre and are removed.
Nitrogen, being a slow permeating gas, has a greater resistance when trying to pass through the fibre walls, and continues through the hollow fibre to be collected and supplied by our system for the use of tyre inflation.
CMS; Carbon Molecular sieve. A similar approach but in this instance, the faster gases are attracted to crystals within a tube leaving the nitrogen to be expelled from the tube and into a receiver. There are two – four tubes in a system which take it in turns to be pressurised with compressed air, release the nitrogen and then get flushed through to remove the fast gases.
Either way, a properly maintained system, using either method will produce a dryness and purity suitable for tyre inflation.