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The tires I bought and had installed at Costco have nitrogen in them. I was not given an option of air vs nitrogen, and there was no extra charge.
I can put regular air in if needed, right? It's not like it's going to explode...
And what is the problem with moisture in the tire? It is very humid here, perhaps that's why the local Costco does nitrogen?
Costco stole my black valve caps and replaced them with ridiculous looking green ones without asking. I don’t care if the nitrogen makes my car float and get 100 mpg, don’t mess with my caps!
Pressure * Volume = n * (Gas-Law Constant) * Temperature
Where 'n' is the mole count of the gas under investigation. It is also directly proportional to the density of the gas which in this case means that the pressure swings are directly proportional to the density difference of Air and Nitrogen.
Under IUPAC standard press. and temp. the densities are:
Air = 1.2754 kg/m^3
Nitrogen = 1.251 kg/m^3
That's less than 2% difference your tires will see in pressure variation under changing temperatures between the two gases.
As for the leak rates... again, effectively identical. The molecular diameter of Air is 0.372 nm compared to 0.375 nm for Nitrogen. Thats a 0.8% difference.
Unless your tires have temp deltas on the order of hundreds of degrees F (like those on aircraft), the only meaningful benefit of nitrogen over air is that it provides an inert environment that will prevent oxidation. For passenger cars, big deal - When is the last time you had a rim or tire rot out from the AIR that you used?
the only meaningful benefit of nitrogen over air is that it provides an inert environment that will prevent oxidation. For passenger cars, big deal - When is the last time you had a rim or tire rot out from the AIR that you used?
It's not for the tires. it's to keep the TPMS sensors from corroding and failing. 50 years ago, we didn't have electronics in our tires. We do today.
99.9% of the time, it really won't matter, but those sensors are the real reason that a number of companies have gone to pure nitrogen as factory fills. If you introduce moisture in the air in the tire, due to moisture in the air compressor or lines, you can introduce a failure point for your TPMS sensors. Just something to think about.
I buy into the idea that nitrogen is free of humidity and humidity degrades the wheel. That's important to me since my tires were purchased in 2008. They are about due to be replaced due to age but there are no cracks in the outside of the tire like you would expect. I almost never have to add air.
Vehicle - 90 GMC 4X4 with 400,000 miles - is kept outside.
Quote:
Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.
Most dealer do not put nitrogen in the tires when the vehicle is being sold. If you buy the vehicle and pay for the nitrogen, they will go through the purge and fill as part of the dealers prep of that new vehicle for delivery to you. If you refuse to pay they will just wipe the charge off the bill and you get the air already in the tire. You would be surprised how many people who refused the nitrogen tires think they still got it for free.
They did.
Air is mostly nitrogen. You get all the nitrogen you need in your tires when you fill them with air, so as long as your tires are not flat, you do get the nitrogen fill for free.
"Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim."
As far as the pressure swing item, the above is flat wrong. Someone needs to go back to high school physics and review the concept of "saturated vapor pressure".
As far as humidity, the process of compressing the air will cause water vapor to condense out of the air as it cools, which will happen in the compressor tank (saturation temp increases with pressure). So if anything the water content inside the tire will be less than that of the air surrounding it from which the air was drawn into the compressor. If a TPMS sensor won't corrode and go bad sitting on the shelf in the parts warehouse, it won't corrode and go bad inside your tire.
I am willing to bet that the number of steel or aluminum wheels that are scrapped due to corrosion originating on the inside, using air (not considering, for example, fix-a-flat) is less than 0.001% of the number that are scrapped due to corrosion originating on the outside from road salt, which I would guess is less than 1% of the number that are scrapped due to collision damage, which I would guess is less than 1% of the number that are scrapped because the whole car is scrapped at the end of its life.
It's not for the tires. it's to keep the TPMS sensors from corroding and failing. 50 years ago, we didn't have electronics in our tires. We do today.
99.9% of the time, it really won't matter, but those sensors are the real reason that a number of companies have gone to pure nitrogen as factory fills. If you introduce moisture in the air in the tire, due to moisture in the air compressor or lines, you can introduce a failure point for your TPMS sensors. Just something to think about.
You replace the sensors when you replace the tires anyway. They cost nothing. They do not corrode in the life of a tire. Maybe in 50 years. However no purge is going to get every molecule of humid out of a tire. The whole thing is a complete scam.
My 1973 Jensen Healey has its original alloy wheels. It have never had any more nitrogen in it than comes free with air. The wheels have no corrosion. None. So I guess it takes more than 45 years of use to benefit from Nitrogen. Maybe in 75 years your wheels will corrode due to the use of regular air. I suspect however it would take more like 600 years for nitrogen to make a difference. If you are concerned about your wheels corroding in less than 600 years, then by all means spend the moeny on nitrogen. If my wheels last 600 years - I am good. I do not need them to last any longer than that.
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