Nitrogen in tires can improve tire performance and longevity

How many times have you left a bike or trailer or vehicle unused for a couple months only to find the tires had deflated? Why do tires leak air?

You just may find the answer in that question.

Our atmosphere is made up of approximately 78 per cent nitrogen and 21 per cent oxygen. All tires will lose pressure over time because the oxygen makes its way through the polymer chains of the rubber in the tire. Even though nitrogen molecules are larger than oxygen molecules, that small concentration of oxygen is just enough to create a dilution of the overall mix, allowing for a greater chance of the air to literally leak between the rubber molecules. This is the norm with tires.

So why not fill tires with pure nitrogen to minimize air pressure loss? If you’re lucky enough to live in driving distance of a service station that offer nitrogen refills, it turns out that you can.

The advantage of nitrogen over oxygen is that the pressure of a tire filled with nitrogen is not affected as much from variations in ambient temperature, or from heat caused by road friction and load. Nitrogen is currently used in aircraft and race car tires for these very reasons. Winter tires filled with air may have a noticeable loss during the season than tires filled with nitrogen.

Nitrogen also has other benefits over regular air. Unlike oxygen in the air, nitrogen is non-corrosive. The rust that forms on the inside of a mounted tire and wheel assembly, is simply the combination of oxygen and iron, or iron-oxide. With only nitrogen inside the tire/wheel combination, there is no way for rust to form.

But for nitrogen to be effective in the everyday automotive world, the rims must be free of corrosion on the tire to rim sealing surface, whether steel or alloy. This "corrosion-free" state may be hard to achieve on anything other than new or low-use rims that haven't seen wintertime road de-icing chemicals. Otherwise, the nitrogen will leak out the same as air.

Oxygen and moisture also contribute to the degradation of rubber in tires. Generators used to fill tires with nitrogen remove both oxygen and moisture. Therefore, the inside rubber portion of the tire should degrade slower.

But the downside of nitrogen is that there’s usually an added cost when filling your tires with nitrogen, whereas air is (usually) free. There’s also not much in the way of infrastructure support for refilling your tires. In other words, not a lot of service stations offer this service. But if you’re looking for better tire performance, and longer tire life, it might be worth going out of your way to find a station that does.