Don't get scammed into putting nitrogen in your tires for 40 bucks

[NNN0LHI]

http://www.chicagotribune.com/business/autocorner/chi-mxa0727nitrogenjul27,0,907521.story

Free air same as fee nitrogen as long as your tires are properly inflated

By Bob Weber | Special to the Tribune
1:53 PM CDT, July 24, 2008

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?

[hobbit709]

1. You can buy a whole cylinder of nitrogen for less.

[alarimer]

2. Air is already 79% Nitrogen

only 21% (or close to that) oxygen. So you are already filling your tires with mostly nitrogen.

[HamstersFromHell]

3. It does have big benefits, but...

definitely not worth $40, unless you bought expensive premium tires and want 'em to last without checking pressures regularly.

Most places in this area offer it free with tire purchases.

Part of it's benefit is the permeability issue, but the rest is a tire inflated with pure nitrogen will gain (or lose) far less pressure when heated and cooled.

You car's tire sticker lists the COLD inflation pressure...as in car's been sitting in the garage overnight and not driven. Now, add the heat of a hot sunny day, hot pavement and the tire's flexing while rolling and it generates (and absorbs) a lot of heat. Roughly, each 10 degree change in temperature will change the tire pressure 1 psi. And 2-3 psi underinflation will cost you a few percent in gas mileage. Severe underinflation will not only cost you mileage, but traction, stability and tire life. But how many folks regularly check their tires?

That tire that the sticker says 26psi cold means after driving 20 miles, you can expect the pressure to be 2-5 psi higher...where it's in it's operating range. If you checked it hot and set it to 26psi, then the tire is already quite underinflated, and even more so when cold. (Remember all those Ford Explorer tire failures? Partly bad tires, partly Ford saying 26psi...way too low for such a heavy vehicle, but it made it "ride nice" on those underinflated tires.)

Nitrogen filling will all but eliminate the temperature expansion differences, giving you much more consistent wear and handling characteristics, and increasing gas mileage from not having to "bring the tires up to temperature" to achieve proper inflation for good mileage.

As an extreme example, when motocross motorcycles started the changeover to the then-new Fox Shox (no springs, just twin air bladders) around 1977, my friend bought a pair. Filled 'em at a scuba supply house, because no one else could provide the pressure necessary to give proper spring rates. (Top bladder at 250psi, bottom bladder at 125) On an 80 degree day, after 10 minutes of riding, the heat generated by the shock movement increased the pressure of plain old compressed air to the point the suspension was locked rigid...well over 300 psi in the tops and over 200 in the bottom bladder. He leased a nitrogen bottle, bled the shocks and refilled...no problem, the shocks were remarkably consistent from then on due to nitrogen's stability under temperature extremes.

[Pierre.Suave]

5. Thanks for typing that all out

so I did not have to.

[pokerfan]

6. It's not the Nitrogen per se

Part of it's benefit is the permeability issue, but the rest is a tire inflated with pure nitrogen will gain (or lose) far less pressure when heated and cooled.

Nitrogen gas behaves the same as any other gas. PV=nRT isn't dependent upon the element involved.

It's the moisture (humidity) in the Nitrogen/Oxygen mixture when plain ol' air is compressed that is the major factor but it's pretty marginal for normal consumers. It is important in motor sports where they might care about fractions of a PSI.

http://www.straightdope.com/columns/070216.html

[Blue_Tires]

4. for the most part, its only good for racing applications

[ashling]

7. Tastes more like real Dr. Pepper

:rofl: