Nitrogen in Tires

Should You Really Put Nitrogen in Your Car Tires?

There are several compelling reasons to use pure nitrogen in tires. But it's not a must-have.

By Ezra Dyer
BRIAN SILVESTRO

Is there really an advantage to using nitrogen rather than air in car tires, such as better fuel economy, a smoother ride, or longer tire life? Well, sort of.


From the top: Air is 78 percent nitrogen, just under 21 percent oxygen, and the rest is water vapor, CO2 and small concentrations of noble gases such as neon and argon. We can ignore the other gases.

There are several compelling reasons to use pure nitrogen in tires. First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.

Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.

YOUR TIRE PRESSURES WILL REMAIN MORE CONSTANT, SAVING YOU A BIT IN FUEL AND TIRE-MAINTENANCE COSTS

How is water relevant to a nitrogen discussion? Any system that delivers pure nitrogen is also going to deliver dry nitrogen. Filling tires with nitrogen involves filling and purging several times in succession, serially diluting the concentration of oxygen in the tire. This will also remove any water.

So, there are the benefits: With nitrogen, your tire pressures will remain more constant, saving you a small amount in fuel and tire-maintenance costs. There will be less moisture inside your tires, meaning less corrosion on your wheels. But if your tires were filled with nitrogen (denoted by green valve stem caps) and you're low on pressure, don't be afraid to bring up your PSI with regular old air.

You also shouldn't let your nitrogen-filled tires lull you into complacency when it comes to checking air pressures. "Nitrogen is no substitute for proactive, regular tire care and maintenance," says Keith Willcome, Consumer Tire Engineering, Bridgestone Americas Tire Operations. "Bridgestone does not prefer oxygen or nitrogen—both are acceptable gases for tire inflation. Both air and nitrogen respond similarly to The Ideal Gas Law, which says temperature and pressure are directly related. For tires, this means every 10 degree change in ambient temperature will result in approximately 1 psi change in tire inflation pressure. This change is the same for nitrogen inflated tires and tires inflated with air. Proper inflation pressure is key to tire safety and performance."

So check those tire pressures at least once a month, no matter what's inside.