Some tyre specialists now offer to inflate your tyres with pure nitrogen, and charge extra for it.
Purified nitrogen has been used to inflate tyres on aircraft and racing cars for many years but does it really make sense for ordinary car tyres?
The air we breathe, and the compressed air normally used to inflate tyres, is mostly nitrogen anyway – 78% Nitrogen, 21% Oxygen and 1% other gases.
For passenger car tyres the main claims for pure nitrogen seem to be:
- Less corrosion – because unlike air there's no moisture in pure nitrogen
- Slower rate of pressure loss – because the nitrogen molecules are larger than the oxygen they’ve replaced.
Your tyres can lose air:
- Through the inner lining of the tyre
- Because of a faulty or dirty valve
- Because of punctures, or
- Through failure of the seal between the tyre and the wheel rim
Pure nitrogen might leak more slowly through the liner, but you’d still have to check the condition and pressure of your tyres regularly.
- Corrosion is unlikely anyway with normal compressed air because only the outer tread band of a car tyre contains steel – the amount of moisture reaching it from the inside is minimal.
- To change to nitrogen, the air already in your tyres has to be removed first.
- There will usually be a one-off charge per tyre but once filled with nitrogen, future top-ups would have to be with nitrogen if any advantages are to be maintained.
Overall, while accepting the possibility of purified nitrogen being of benefit in certain applications, we don't think that the cost and possible inconvenience are justified for normal passenger car use.
Aircraft and motorsport
At cruising height, temperatures may be as low as -40C and any moisture in aircraft tyres can freeze causing vibration and balance problems when landing.
- Pure nitrogen is dry so eliminates this problem.
- Using dried compressed air could achieve the same thing.
In motor sport, they use pure nitrogen (or dried compressed air) to eliminate moisture in tyres which helps reduce tyre temperature at high speeds and loads.
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(updated 30 August 2019)