Blue Line


December 3, 2012  By Dave Brown

915 words – MR

Nitrogen-filled tires

The biggest consumer scam in decades

by Dave Brown

It’s been an interesting week. A Nigerian prince is giving me part of his fortune if I help him smuggle it out of his country. All he needs is my banking information. Now my local garage wants to fill my car tires with nitrogen. I’m going with the Nigerian prince.

began researching the issue of filling tires with nitrogen instead of air when we were asked about the possible benefits for police vehicles. The answer is… there are no benefits. Nitrogen has only one purpose – to pad the bottom line of dealers and tire shops. There is absolutely no scientific basis for claims of its benefits and most so-called “studies” turn out to be performed by the very companies who supply the equipment to garages.

You’re better off sending your money to Nigeria; at least they don’t try to snow you with junk-science before they rip you off.

Nitrogen-filled tires became trendy when people found out race teams and airlines fill their tires with nitrogen because it’s more stable in extreme temperature changes. Companies suddenly sprung up to flog what is essentially a compressed gas version of snake oil and garages and tire retailers quickly hopped on board, looking for anything that would increase profit margins.

Large aircraft tires are filled with nitrogen because they can go from minus 100 degrees to plus 200 degrees C in seconds; nitrogen is less prone to expansion and contraction during these ultra-wide temperature variations. On an aborted landing, hot aircraft tires must fit into tight wheel wells with only fractions of an inch to spare.

Nitrogen is manufactured as an inert gas; air in an exploding aircraft tire would tend to increase combustion to a nearby fire while nitrogen would tend to decrease combustion.

Car tires never experience such extreme temperature variations so why are so many people suckered into paying for what is essentially filtered air?

Sellers use pseudo-scientific language that relies on people discarding common sense. The most common argument, “nitrogen molecules are larger and nitrogen-filled tires are less prone to leakage,” makes no sense. Anyone who tries to tell you this has absolutely no concept of the size of a molecule. I wasn’t always awake in physics class but I do remember that 10 million molecules take up less space than the period at the end of this sentence. Saying bigger molecules are less prone to leakage would be like saying one could empty the St. Lawrence faster with a coffee cup than with a thimble.

In fact, nitrogen molecules are only 3 per cent larger than oxygen molecules (they are side-by-side on the periodic table.) Air is comprised of 78 per cent nitrogen, 21 per cent oxygen and one per cent other gases. The purest form of nitrogen one could conceivably manufacture outside a laboratory is about 95 to 98 per cent nitrogen so essentially they’re selling plain old air.

Even if it was true that nitrogen molecules leak less than oxygen molecules, I still wouldn’t need to fill my tires with expensive nitrogen; I’d just have to wait a few weeks for all the oxygen molecules to leak out and I’d be left with pure nitrogen – for free.

Some people know nitrogen may have only marginal benefits but feel it can’t hurt because it didn’t cost them anything. “They put nitrogen in my new tires for free.” Trust me, nothing is free. Those lime green valve caps, the 25 cents worth of nitrogen and a huge profit margin were all built in to the cost of the tires.

asked a pro racing driver why race teams use nitrogen. He explained how the handling of a lightweight race car can change drastically with only tiny differences in tire pressure. If nitrogen offers even the slightest advantage at race speeds, they will take it. “Besides,” he said, “nitrogen tanks show up at our pits all shiny and clean and filtered. We know it doesn’t make the slightest bit of difference even at the speeds we run but it is there for us and we don’t have to do anything.”

If your average garage doesn’t filter or properly maintain its air compressors, what makes you think they will keep their nitrogen tanks in pristine condition?

Several garage owners we talked to admitted nitrogen offers no benefits. Asked why he sells it, one owner simply said, “Competition. If the store down the street puts it in all their tires, we need to as well. We can tell customers they are just as good standing in the middle of a street tearing up ten dollar bills, but if they insist, we put it in.”

Not every garage agrees. One Winnipeg tire retailer refuses to sell nitrogen. “We think it’s not just a waste of money, it’s dangerous. Those green valve caps give people a false sense of security.”

The next time your service station tries to sell you on the benefits of nitrogen by saying it improves mileage, point out that it is properly-filled tires that save fuel and improve handling. It doesn’t matter if they are filled with air, nitrogen or cow flatulence; 35 psi is 35 psi.

So what colour are your valve caps?

“Nitrogen? We love that stuff!” one local garage owner said. “It’s our inside joke. When we see those green valve caps come through our shop door, we know we can sell that person ANYTHING!”

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