Why do we fill tires with air?

Nitrogen in tires: is the expensive gas worth it?

The tire dealer's offer sounds tempting: Instead of air, they fill the tires with nitrogen - and the tire pressure remains constant for a long time. But is that true? And what about the costs?

  • Expensive filling: nitrogen instead of air

  • The promise: Less pressure loss

  • But: tire gas hardly has any advantages

Tire dealers are vigorously promoting it: all four tires are completely filledNitrogen or so-called tire gas costs around 12 euros. In return, the car tires should then lose less pressure and hardly need to be checked. Nitrogen is even said to have a positive effect on wear and tear and fuel consumption.What is it about the promises?

Nitrogen for aircraft or racing tires only

It is true:nitrogen has due to theslightly larger moleculeshas a worse diffusion coefficient than oxygen and therefore escapes a little more slowly from a tire But tests showed that the pressure differences between air and nitrogen-filled tires were only within a few hundredths of a bar of tire pressure even after several months - a difference that is hardly worth mentioning.

Another argument in favor of a nitrogen filling is thelower risk of firecited. That is why the tires of commercial aircraft, Formula 1 cars or even dangerous goods transporters are usually includedNitrogen instead of airfilled.

That makes sense, because these tires are exposed to extreme loads and could start to burn in the event of extreme accelerations in the event of a defect or significantly insufficient air pressure.

nitrogen however, has the advantage that he not flammable is and - hence the name "nitrogen" - evenChoked fire. oxygen on the other hand, is the basis for every open flame, so it has a fire-accelerating effect.

This advantage is howevernot transferable to normal car tires.The temperature loads on tires that occur in Formula 1 racing and when aircraft are landing are far from being reached in road traffic.

Nitrogen in the tire gas

Commercially available "tire gas" usually has oneNitrogen content of about 90 percent.For comparison:air- and thus also the compressed air - contains about78 percent nitrogen.Nitrogen is obtained on an industrial scale by liquefying air using the Linde process. A relatively inferior quality with residual oxygen is sufficient for tire gas, since car tires are usually not flushed with nitrogen and therefore always contain residual air and thus residual oxygen.

Tire pressure control remains necessary

So if you assume that thepressure loss caused by diffusion on an intact tire for an estimated 3 months0.1 barit becomes clear that this cannot be the reason to reduce the regular tire pressure checks. Because other possible pressure losses e.g. throughLeaks and damageplay a much bigger role.

The specific properties of the filled tire gas have no influence on this pressure loss, because any gas escapes through a hole in the tire! Filling with nitrogen does not release you from the obligation to regulate the pressure regularly - i.e. about every two weeks -to consider.

Because withcorrectly set air pressureEven negative influences on wear and tear and fuel consumption are excluded, it quickly becomes clear: The price advantage clearly speaks in favor of filling from the normal compressed air compressor.

Even more: The statement that you can extend control intervals in connection with "filling gas" is dangerous, as it ultimately leads to a more carefree handling of the obligation to check tire pressure. And that is why we do not recommend the standard use of tire inflation gas.

Our conclusion:Tire gas is not worth it!If you regularly check the tire pressure and fill it with normal air, you can save yourself the more expensive nitrogen!

Technical advice: TET.

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