Nitrogen versus air in tires

Does the cost of filling your tires with nitrogen outweigh the benefits? Probably not.

Lots of experts (and plenty of people who are selling nitrogen) make consistent and valid points about the benefits of filling your tires with nitrogen instead of regular old (and generally free) air.

The pros:

• While air is about 78% nitrogen, it also contains oxygen – as much as 21% -- and water vapor.  And the water in oxygen helps contribute to “oxidative aging” in tires that can negatively impact tire life. Water inside your tires can corrode aluminum rims or rust steel rims.
• Tires for big rigs cost about $480 when you factor in two retreads. The average life span for a truck tire is about 270,000 miles. Using nitrogen instead of air reportedly helps the casings from failing prematurely and allows for multiple retreads. One source says by using oxygen, the tire life can be extended as much as 25%. That means your tires could take you as much as 330,000 miles for a savings of about $120 per tire.
• When it comes to nitrogen, size matters. Here’s why: nitrogen molecules are larger than oxygen molecules. That means tires leak less of the gas over time. Therefore, tires filled with nitrogen tend to retain their pressure levels better and longer than those filled with regular air.
• Nitrogen heats up more slowly than air, which means your tires are running cooler. Not only does that help with wear and tear, it also helps lower your risks of having a high-speed blowout during hot weather.
• One fleet test in Canada showed that tires filled with nitrogen helped with fuel economy – improving it by 3.3% as well as substantial improvements in tread life mentioned above.

The cons:
• If you fill with nitrogen, you should never “top off” with air.  By adding regular air, you’d lose most of the benefits of nearly-pure nitrogen because the oxygen molecules contain water vapor and because the oxygen molecules are smaller which means they can leak more easily.
• Nitrogen is more difficult to find than ordinary air.
• Nitrogen is more expensive than air. Some service stations or tire dealers charge as much as $15 for car tires filled with nitrogen.  Filling truck tires will certainly cost more.

So what do you think? Share your thoughts or experiences with nitrogen-filled tires here:

Checking Tire Pressure

When manufacturers make recommendations on tire pressures, their figures are based on cold tires. The best time to check tire pressure is after they’ve been resting overnight or at least for several hours. The ideal temperature to get the most accurate reading on tire pressure is about 70 degrees Fahrenheit.  And the best place to do it is somewhere near sea level.

A low-cost tire pressure gauge may not be your friend. You get what you pay for and the cheap ones often are not calibrated accurately. The better bet is to invest in a self-calibrating, electronic digital gauge. These hand-held units are reportedly the most accurate.

Tire pressure facts:
• Severe heat and extreme cold impact tire pressure.
• Increase the temperature from 70 degrees F to 100 degrees F and tire pressure goes up. Driving even short distances increases it even more.
• In cold weather, tire pressure automatically drops.  At around freezing, tire pressure will be at least a few pounds less, and when the temps hover closer to 0, even less.
• With less oxygen in the air, tire pressures change at high altitudes.  For every 1,000 feet above sea level, you will see a corresponding increase in your tire pressure of about half a pound. As an example, take your rig up to 5000 feet and your tire gauge – which was accurate at sea level – will now show your tire pressure to be 2.5 psi too high.

Tire pressure tip:
• Changing out a tire? Be sure to check its pressure right away and perhaps a day later. Sometimes a bead sets slowly and the tire gets overinflated or it could have a small leak and be underinflated.

Got any tips or tricks on how you keep your rig’s tire pressure at the right level or when you check it? Share them here: