Given that the average tire loses up to two psi per month, not to mention seasonal temperature/pressure changes, tire pressure is one of those things that should always be on your radar. Proper tire pressure impacts fuel economy, handling and tire-wear patterns.
A few decades ago, the racing industry stumbled across the benefits of nitrogen vs air in tires. They found that nitrogen was less-affected by temperature than normal atmospheric air. Atmospheric air is made up of a mixture of gases, about 78 percent N2, 21 percent O2 and 1 percent trace gases, such as H2O, Ar, CO2, Ne, He and CH4 (nitrogen, oxygen, water vapor, argon, carbon dioxide, neon, helium and methane).
Nitrogen vs Air in Tires: What’s the Deal?
When it comes to maintaining tire pressure, it’s all those other gases, particularly O2, H20 and CO2, that don’t lend themselves to pressure stability. Oxygen, for example, is slightly smaller than nitrogen, and it passes right through the walls of your tire, that is, in between the chain-molecules of the rubber, not to mention squeezing between the tire and the wheel, the valve stem and the wheel or past the rubber seal in the valve core. Additionally, O2, H2O and CO2 expand and contract more than N2 when the temperature changes, and are also slightly corrosive, oxidizing steel and aluminum wheels and accelerating the aging of the rubber in the tire.
On the other hand, one can fill tires with pure nitrogen, avoiding the problems of seasonal expansion and contraction, “normal” pressure loss over time and corrosion, but you also have to pay more. You may have to pay as much as $10 per tire to put pure nitrogen — 95 percent or better — in your tires, whereas you can get “regular” air for free, or maybe $1.
Here’s a quick a breakdown of the advantages and disadvantages of each:
|Up to $50.||Maybe $1 (or free).|
|Requires expensive special equipment.||Requires no special equipment or training.|
|Could take 30 minutes.||Could take five minutes.|
|Available only at some dealerships and tire shops.||Available everywhere, even in a $20 bicycle pump.|
|Almost unaffected by temperature.|
Tire pressure remains stable season to season.
|Sensitive to temperature.|
Tire pressure drops in the winter.
Traction and fuel economy suffers.
|Nitrogen molecules slightly larger than oxygen molecules.|
Harder to "slip through the cracks" in the rubber. Tires maintain pressure longer.
|Oxygen molecules slightly smaller than nitrogen molecules.|
They slip more easily through the rubber of the tire. Tires constantly lose pressure.
|Nitrogen is dry, almost no water vapor. Wheel corrosion nearly eliminated.||Air can be wet, particularly if the shop doesn't have properly maintained system dryers. Wheel corrosion possible.|
|Because tire pressure remains more stable, you'll spend less time checking and adjusting your tire pressure every month, and your fuel economy remains stable.||Because tire pressure continuously fluctuates, you'll have to keep up with weekly tire pressure checking and adjustment. Fuel economy also fluctuates.|
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Photo courtesy of Foter.
Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.