What started as a fad just a few years ago has ballooned into a profitmaker for tire dealers and a head scratcher for tire buyers: nitrogen inflation.
Nitrogen is colorless, odorless, safe and ubiquitous. Nearly 80 percent of the air we breathe is nitrogen. Unlike air, which contains oxygen, nitrogen won’t support combustion so it has been used in critical situations for years: In aircraft tires, including Air Force One and the Space Shuttle. The military uses it in many vehicles as does NASCAR.
But is it worth up to $40 to inflate your car’s tires with it?
Perhaps the biggest benefit from nitrogen is that its larger molecules are less likely to pass through the rubber than oxygen molecules. Yes, rubber is permeable. Think about that helium filled balloon that clung to the ceiling yesterday, but fell to the floor overnight. According to the Get Nitrogen Institute, with 95 percent nitrogen in your tires, they retain optimal pressure three to four times longer.
Four times longer than what? Air? Oxygen? Frozen custard?
“The reports I have read, indicate that pure oxygen permeates through a tire at a rate of three to four times faster than pure nitrogen,” said Woody Rogers, Product Information Specialist at The Tire Rack, America’s largest independent tire tester.
“But the air we breathe and fill our tires with is made up of about 78 percent nitrogen, 21 percent oxygen, and 1 percent other stuff. So only 21 percent of what you inflate the tire with escapes. The majority of what is normally in the tire [nitrogen molecules] escapes at the slower rate.”
Still, underinflated tires waste energy. If you ride a bicycle, know how much more work it takes to pedal on low tires. But how much does fuel economy suffer from underinflated tires?
“Measuring the impact of underinflated tires is difficult to impossible,” said Rogers. “How you drive seems to have the biggest effect on m.p.g.”
But easier to quantify are the safety risks to the vehicle occupants.
Underinflated tires flex constantly, which can lead to catastrophic tire failure, what used to be called a blow-out, which according to National Highway Traffic Safety Administration statistics have become relatively rare. Then there is the risk of changing a tire along the side of the road.
Some people won’t take that risk on a busy highway, but instead will hobble along to the nearest exit or other safe area. Doing so usually ruins the tire; doing so for enough miles will kill the rim too.
It costs much more to replace a tire than you gain from improved your rolling resistance from a tire properly inflated with nitrogen or air said Rogers, adding that “Checking your tires is cheap insurance.”
There are about 9,800 stores where you can find nitrogen but you may want to consider availability, especially if you live far from a metropolitan area. Charges range from $4 to $10 per tire.
Of course, at most stations, you can still fill your tires with air for less than $1, if that.
In the industry, there has been some question lately as to whether one of the big tire retailers will offer free nitrogen as a marketing toolway to gain a market advantage.
Your tires do not require nitrogen, but there are advantages. For more advantages and a fuel savings calculator go to www.getnitrogen.com.
“There are two things I strongly believe in,” said Rich Lucas, president of Lucas Tire & Auto on North Western Avenue in Lakeview, “snow tires and nitrogen. I’ve seen lots of fuel saving gimmicks in my 40 years in the industry and this is definitely not a gimmick.”
Lucas charges $7.50 per tire for nitrogen, but plans to soon start offering it free. “We used to give away oil changes, but we think this will be much better,” said Lucas who sees it as a way to boost the take rate from the 8 percent of customers wanting it.
“Only about two people have asked my about nitrogen in the last two years,” Dale Gervais, owner of Prairie Tire and Auto in Chicago Heights, said of the slow demand. “My customers don’t want to pay extra for it so I can’t justify the cost of the equipment.”
But it really doesn’t matter whether you use air or nitrogen as long as you properly inflate — and you can find the manufacturer recommended inflation on a sticker on the driver’s side door.
“Nitrogen can do no harm unless it’s used as a substitute for proper maintenance,” said Rogers. “Most tire manufacturers will only go as far as saying it’s OK to inflate a tire with nitrogen,” advised Rogers.
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Rubber soul
Tires are the only part of the car that touches the ground, with a contact patch the size of only a playing card. With what’s riding on them, here’s what you need to know about tires and some things we just wanted to tell you:
–Keep tires inflated to the recommended pressure. Don’t know what that is? Check the sticker on the driver’s door jamb.
–When is it time to replace your tires? When the wearbars — or Lincoln’s hairline — show.
Wear bars are molded into the tire and revealed when the tread is less than two-thirtysecond of an inch. This is the same measurement from the edge of a penny to the top of Lincoln’s head. So if you put Abe upside down in a tread and see his hair, you need new tires. Some marketers now suggest that you use a quarter instead of a penny, saying it is safer to replace the tires before reaching the legal minimum tread.
It may be hot now but remember, tires lose 1 pound of pressure for each 10-degree drop in temperature.
–Age before duty? There’s a school of thought that you should replace tires every 6-7 years regardless of mileage – and stores are not allowed to sell tires older than 10.
How to tell your tire’s age? Look at the small print at the center of the tire. There you’ll find the number of tread plies and sidewall plies and what they are made of. The maximum load is usually spelled out in metric (kg) and customary (lbs) followed by the maximum inflation pressure, again in metric (kPa) and customary (psi) terms. The type of construction (radial in our graphic) and design (tubeless) information also is usually molded into the rubber. Then there’s a DOT and numbers following it refer to the safety code and may include a code for the manufacturing plant as well as the date of manufacture. The three-digit code prior to the millennium shows week and year (e.g. 457 would be 45th week of 1997. After 2000 it is a four digit code — 2305 would be the 23rd week of 2005)
–Bob Weber
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Bob Weber is an ASE-certified Master Automobile Technician, having recertified every five years since 1978. Contact him at motormouth.trib@verizon.net.
See related story, “Treading rightly with your tires,” Transportation section, Page 5
