NITROGEN IN CAR TYRES: What's the point of filling car tyres with Nitrogen?


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 are 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 across 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.

In tests, that 20% Oxygen / 80% Nitrogen mix changes to a 10% / 90% mix in a tyre that has aged  and not been toped up recently. This demonstrates that the oxygen is leaving the tyre cavity faster than the oxygen so why not start with a higher Nitrogen concentration to begin with? It is true to say that regular tyre maintenance negates the need for Nitrogen inflation but unfortunately, a huge majority of motorists don’t do this resulting in under inflation.

Under inflated tyres create drag which increases tread wear, fuel costs and the risk of punctures as well as having a significant effect on a car’s performance both in handling and cost. By having your tyres inflated with nitrogen this produces a stable inflation mixture, as can be seen in the diagram attached, that has improved pressure retention properties that will ensure tyres remain fully inflated for longer.

By having your tyres at the correct pressures you will experience the following benefits:

1. Better handling and road holding
2. Reduces tread wear and increases tyre life by up to 25%
3. Correct inflation pressures reduce puncture risk by up to 33%
4. Reduced rolling resistance improves miles per gallon by 2%

Nitrogen tyre inflation is not a new concept. Nitrogen as a tyre inflation medium has been around since the early 70’s and has been used in applications which require safety or performance. The earthmoving industry use Nitrogen to prevent latent heat build-up as Nitrogen does not heat up as much as compressed air when a vehicle is in motion. Similarly, there is an Airworthy Notice posted to say that all aircraft must have a minimum 95% Nitrogen in their tyres. This was issued following 3 aborted take offs by an air Mexico flight, cause so much heat in the tyre that when it was retracted into the undercarriage the combination of heat and oxygen cause the tyre to explode.

Formula 1 Grand prix racing have used Nitrogen for decades as the tyre pressures are so critical and nitrogen is a dry, inflammable gas. Standard compressed air, contains 78% Nitrogen, 21% Oxygen and 1% other gases. It also contains water, both in free form and as vapour. At tracks like Monza, the tyre cavity can reach temperatures of 180 degrees centigrade and at this temperature water can expand to 1000 times its original size, greatly increasing tyre pressure. As there is no control over how much water enters the tyre a driver would have 4 tyres, at various different pressures, while doing close to 200 miles an hour.

For the majority of general motorists, Nitrogen inflation machines provide a solution to the gradual pressure loss which requires air top ups every 2 weeks, and will maintain the correct pressure, correct contact patch and provide safer and more cost efficient motoring.


Value my car