It does nothing, except make the seller a little money. Many bogus claims are made that are nonsense. A problem with it is that folks might be reluctant to fill up with 'plain' air once they put nitrogen in their tires, causing problems instead of solving them. Even if it was true that air leaked more rapidly (it doesn't except at year-type intervals), it would, according to them, be the oxygen leaking out, leaving the nitrogen behind, so after a few times of filling up you'd be achieving what they're selling, nitrogen in your tires!
Well, it inflates the tires, but regular air does that, too.
Nitrogen may be worthwhile if your vehicle has a tire pressure monitoring system with inside-the-tire pressure sensors, since pure nitrogen should not have any water vapor, which air has. Otherwise I don't see any benefit.
"...pure nitrogen should not have any water vapor, which air has."
True, but it hardly matters. Air at 20C and 50% RH actually has about 1.5% water mixed in on an absolute level. Even on a very cold day when the water condenses, the change in pressure can't be noticed.
It is a sales gimmick or it is just a way of making more money. What they say is true, but it is just not a meaningful difference The higher percentage nitrogen mix (it will never be 100%) may loose air a little slower, but over the entire life of the car, it is unlikely to make a measurable difference. Same with all the other things they say about it.
However it does tell you something important. You know the places that are advertising the stuff should not be trusted.
Wheels that are made for Nitrogen use have two valve stems. One is used to take the air out as the Nitrogen is pumped in. If your car has only one valve stem, you end up with a mixture of Oxygen and Nitrogen, which is what you get with normal air. Save your money.
Joseph is right. Only disreputable businesses will try to sell you Nitrogen for your tires. If this is happening where you are currently getting your car serviced, it is time to look elsewhere for an honest service provider.
I though the OP was refering to doing something to his tires with Nitromethane. In automobile circles I've never heard of "Nitro" being anything else. Although some folks (mostly the import crowd) don't seem to know the difference between Nitromethane being used as fuel and Nitrous oxide (NAWWWWAZZZZ!!!) )
You can find different points of view if you "google" nitrogen for tires. There is some talk in adding a required use of nitrogen for tires in CA. Many people who make the laws have been convinced it is a path to using less fuel along with mandantory tire air pressure checks everytime your car is in the shop,the pressure check is the law.
Every scam has its boosters. There is absolutely no basis for claims of improved milage or better ride. Check pressures? Sure, but N2 has no benefit for that.
I think the Nitrogen thing started with aircraft tires. They have a brutal duty cycle...they are hard-frozen at sub-zero altitudes, then have to spin up from 0 to 150 mph in a fraction of a second when they hit the pavement. I was told that aircraft use NI for three reasons:
1) Will not oxidize the inner tire carcass...aircraft use recapped tires, so it pays to keep the carcass in good shape.
2) The expansion coefficient of NI is less than atmospheric mixed gas. In other words, the tire pressure has less variance between cold and hot temps.
3) NI is inert and will not support combustion in the event of a tire explosion in the wheel wells while surrounded by hydraulic lines.
I heard those reasons, too, same reasons apply to race cars. However, #2 is not correct, both N2 and O2 have the same expansion coefficient. Only difference could come from any water vapor that's condensed, but this would only apply some of the time, and would be a very small effect.
The main benefit about nitrogen isn't so much about what it does as it is about what it doesn't do- it doesn't migrate through the rubber. This isn't so much of a benefit on the ground as it is at 35000 feet, where the atmospheric pressure is practically nil. That's an additional 15 psi or so tire pressure to force the lighter components of air (if an aircraft landing gear tire were filled with
air), such as Oxygen, Argon, etc. out of the tire. But, like I said, migration of lighter components of air isn't as big a problem due both to the smaller pressure difference between a vehicle's tires and the atmosphere (on the ground), and the proper maintenance practice of checking tire pressure once a month.
As far as expansion rates, ALL gases, including Nitrogen, have the same thermal coefficient of expansion. Nitrogen appears to have a lesser one because it doesn't migrate through rubber, unlike the lighter components of air.
If I may get on a soapbox, it is truly tragic that general understanding of basic scientific knowledge has diminished to the point where politicians can be easily BSed into requiring us all to buy something we don't need.
I agree wholeheartedly that the lack of basic scientific knowledge in the general population is a tragedy. Although there could be EXTREME conditions recommending use of nitrogen, these don't occur in cars. One claim in particular: your tire won't lose pressure as fast. Unless you're filling with helium, this shouldn't be a problem. Even if it were true, stop and think. With air containing 80% N2, the tire supposedly leaks mainly O2 so you're now up to 90% N2. Top off the tire with air and your'e replacing that lost O2 with 80%N2. After topping it off a few times, even if this were true, you'd end up with higher than 95% N2 anyway.
Be careful how you throw this stone. Scientific knowledge isn't all that universal. If I may illustrate the point:
Most pressure loss occurs between the rim and the tire, not through the tire.
Also, the Partial Pressure Law of Gases works for tires as well. Example: If you have a tire filled with pure nitrogen, oxygen will leak back into the chamber. Put another way, you don't wind up with a high concentration of N2 when you start with air - at least at the pressures used in car tires.
BTW, did you know that airplane tires are sometimes inflated to over 300 psi? So when traveling at 30,000 feet, the difference in pressure can almost be ignored.
Now this is interesting. I've always been curious as to the leakage rates of various molecules through butyl rubber since this nitrogen cra... I mean stuff started. According to this- http://www.velonews.com/article/87175, it appears as though oxygen is less likely to permeate than nitrogen. I'd be interested in your opinion.
snip
Butyl rubber dominates the market and is used for almost all tubeless tires and bike tubes as its permeability to air is incredibly low — butyl tubes have only 10 percent the leakage rates of natural latex rubber tubes.
Permeation by diffusion predicts gas leakage rates proportional to the inverse of the square root of their molecular weights. Using air as a reference the predicted leakage rates for common gases are: helium 2.7, air 1.0, nitrogen 1.02, oxygen 0.95, argon 0.85, carbon dioxide 0.81.
It turns out however that the leakage rate of CO2 is huge, and the reason is that it is actually soluble in butyl rubber and is thus not constrained to normal permeation loss, it can transfer straight through the bulk rubber resulting in severe tire pressure loss on the order of a single day.
06/30/2009 1:02:00 PM
