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Notes From The Road

Nitrogen for Tires
By Wayne Scraba/

Nitrogen does, however, disperse heat much more quickly than ambient air. What that does is to reduce the heat in the tire. That’s one big reason it sees use in exotic racing machines such as F1 or within the NASCAR ranks. Nitrogen does not support combustion. That’s also why commercial aircraft use and the space shuttle used Nitrogen in their tires. An overheated aircraft tire, filled with compressed air can explode during landing. The resulting damage can prove to be catastrophic. However, in a passenger car (and even in many race machines), the chances of a tire exploding and then catching fire are extremely small.
There’s more to the tire heat scenario: According to the “Get Nitrogen Institute,” a Denver-based non-profit organization which advocates the replacement of air in our tires with Nitrogen, Nitrogen offers more predictable pressure fluctuation. That’s why NASCAR teams use Nitrogen: “Regular compressed air can fluctuate considerably when water vapor is present. Fundamentally air, Oxygen and Nitrogen will all behave exactly the same in terms of pressure change for each 10 of temperature change. However temperature alone is not the whole story.
“Ambient air contains moisture, Nitrogen does not. If moisture is present it contributes to a greater change in pressure simply because at lower temperatures water condenses to become a liquid. The liquid form of water occupies very little volume and contributes only a negligible pressure to the tire. But at higher temperatures, such as those in a running tire, water evaporates inside the tire and becomes a gas that increases pressure in the tire.
“Ambient air contains about 21% Oxygen. Oxygen’s smaller molecular size allows it to permeate through the rubber of the tire. By inflating with Nitrogen, which is much less permeable than Oxygen, the pressure changes due to Oxygen loss are greatly reduced.
“The racing industry is correct; Nitrogen is more predictable. Because Nitrogen is dry it has no moisture to contribute extra pressure changes with temperature. Because Nitrogen permeates out much slower than Oxygen pressure changes due to that leakage are almost eliminated compared with ambient air.”
Racing is one thing, but the real world is another. Any number of studies have shown that the majority of drivers rarely, if ever, check the inflation pressure of their tires, and usually only add air when a tire is visibly low or beginning to go flat. According to Bridgestone research, more than 93 percent of all cars in Europe have under-inflated tires. In fuel costs alone, this under-inflation wastes something in the order of 2-billion plus gallons of fuel annually. And research shows that a similar percentage of cars in North American are operating on under-inflated tires. On a one-to-one level, that can equate to a mileage loss (or gain) of something in the order of 3+ percent per car. In today’s day and age, that isn’t something to scoff at.
Nitrogen, which doesn’t escape easily from the wheel and tire combination can obviously contribute to stabilized tire pressures. But on the other hand, so can weekly tire pressure checks—a job that certainly isn’t difficult, and something anyone can accomplish.
In the end, is Nitrogen for you? It’s your call, but at the very least, check tire pressure regularly.
*This is a revised version of a 2008 article. The original article incorrectly stated that Nitrogen gas is denser than Oxygen or compressed air. We regret the error and have removed the erroneous copy.

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