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nitrogen in tires ?

30K views 58 replies 29 participants last post by  igo-wfo 
#1 ·
Just recieved my srt8 and noticed that the valve caps on the tires are green and have N2 on them. I asked the dealer and he told me he doubts they put nitrogen at the factory in the tires but they can put it in at the dealer for a fee. So do my tires already contain nitrogen and who put it in there. If theres no nitrogen in my tires, why the special caps ? I asked my dealer to double check and he hasnt gotten back to me yet. Thanks.
 
#2 ·
My recommendation...replace the green caps with black and don't bother worrying about whether they have nitrogen or not. Check your tire pressure once a month and save yourself a bunch of money.
 
#4 ·
I can say this much. It works great. Tire PSi stays the same no matter the ambient temperature or if the sun is on them.
As ambient goes up and down so does the tires. Nitrogen filled it stays the same.
It really works well in slicks. Dont have to cover the tires while waiting to be called to stageing lanes.
During the burn out the tires stay the same psi with nitrogen. I like it.
If your has the caps it should have the gas in them.
Its cheap for me. I use alot of nitrogen and have the tanks handy from my HVAC company.
FlatTop
 
#6 ·
I can say this much. It works great. Tire PSi stays the same no matter the ambient temperature or if the sun is on them.
As ambient goes up and down so does the tires. Nitrogen filled it stays the same.
No, nitrogen is still subject to the ideal gas law. Pressure will change with temperature, it's science. :). I posted a rather in-depth article on this subject some weeks/months ago that covers everything and shows that nitrogen really offers no advantage to the typical driver.

Dry nitrogen is more stable than "air" because it's dry, not because it's nitrogen.





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#5 · (Edited)
Here we go again with the nitrogen...

I was present when my Challenger came in on the truck. I watched my dealer deflate my tires and re-inflate them with nitrogen. My dealer also will service my tires with nitrogen for no charge, whenever.

That being said, I have an air compressor in my garage and fill my own tires with just plain old 78% nitrogen, 21% oxygen, ambient air. A 100% nitrogen filled tire will help keep out moisture, have a more stable tire pressure, and is fun to talk about at parties. To the average car owner, it means nothing. You should check your tire pressure on a regular basis whether you have nitrogen or not. For a daily driver, it will not give any noticeable differences.

Aircraft use nitrogen in their tires because it is relatively moisture free. At very high altitude where the temperature can be a few dozen degrees below zero, the moisture can be a problem. This is not germane to regular car tires.

If you are a professional race car driver, you could probably school me on the benefits but I would never notice them in my daily driver.

I say leave the green caps. If anyone asks if you have nitrogen in your tires, you can honestly say yes. 78%


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#19 ·
Very well said, and all facts! Aircraft have utilized nitrogen filled tires for years for the exact reason you stated. In the KC-10, I've seen Total Air Temperatures in the -50s°C while cruising in the northern latitudes at the higher flight levels. Eventually, everything starts cooling, including the fuel and the nitrogen gas in the tires. Nitrogen simply adds some pressure stability while preventing moisture that would freeze in the tire.

Yes, most vehicles now run pure nitrogen in the tires from the factory now days, however I can't attest to Chrysler's practices. The color of the valve stem caps doesn't necessarily mean anything. Tire/repair facilities will sometimes install the green caps during a tire change indicating the tires are filled/serviced with nitrogen. My Saturn Outlook came filled with nitrogen from the factory with black valve stem caps. When I had the tires replaced and the TPS valves rebuilt at Costco it came back with green caps.

As mentioned, the tires are still subject to gas laws regardless of the gas used to fill the tires. A tire sitting in the sun will heat up and the pressure will rise. Below are some general tire maintenance tips I posted in a previous discussion:

General tire maintenance tips:

-Rotate approximately every 5,000 miles
-Cross non-drive wheels. Move drive wheels straight forward.
-Balance on every rotation. A wheel with a slight imbalance that may not have been noticeable while mounted on the rear will become noticeable when mounted on the front through the steering wheel.
-ALWAYS re-torque aluminum wheels within 50 miles after mounting. This includes those who just took delivery of their new Challenger. Go re-torque them, you'll get about 1/8 of a turn before the torque wrench clicks. Torque settings for your wheels are listed in the owner's manual. Never use lubricant or anti-seize unless specified with the torque specification.
-Never use your EVIC for setting tire pressures. It may take several miles until the sensors send the current tire pressure to the sensor/EVIC.
-Adjust tire pressure for outside temperature. The tire pressure will rise 1 psi for every 12°F outside temperature with air and 1 psi for every 10°F with nitrogen. If you haven't adjusted the pressure since winter, your tires are over-pressurized.
-Adjust tire pressure when cold. If not possible (warm tire), add 5 psi to the factory (door label) pressure setting.
-NEVER set the cold pressure indicated on the tire sidewall. This is the MAX pressure setting to remain within the designed structural limit of the tire. This does not account for the weight of the vehicle. Always set the manufacturer's labelled (door sticker) pressure for proper tire wear and contact patch with the road.
-Do not set tire pressure when tires have been sitting in the sun. The tires will be hot and won't provide accurate readings. Always set the cold pressure when the tires are in the shade during the coolest part of the day.
-Never run directional tires backwards. This may seem like common sense, but I've seen it several times. For proper rotation of directional tires, the two non-drive tires must be dismounted, flipped, and re-mounted during the rotation.

Whether it's air or nitrogen, you'll be fine, regardless of the original gas type in the tire. If they are low, you can add air to a nitrogen filled tire.

For some additional reading, here is more than you ever want to know about nitrogen filled tires: http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191
 
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#7 ·
Yeah, I don't buy into the whole nitrogen thing either for daily driver cars. I work on Advanced 5th Gen Fighter Aircraft for the Air Force, we use it on them to some extent, but for my car and truck? No....
 
#9 ·
#13 ·
Had to dredge this topic up (no sense creating another one) since I just got new tires yesterday and the topic came up in the waiting room. One thing that I've often thought, that I never hear mentioned, is this. I've heard the argument that oxygen leaks through the tire faster than nitrogen because, even though the molecular weight of the oxygen molecule is more, the physical size is smaller, allowing it to permeate the rubber faster than nitrogen. So... your tires stay inflated longer with nitrogen.

But... think about it. If that's true, then each time you put air in your tires, more oxygen has leaked out than nitrogen. That should increase the percentage of nitrogen in your tires naturally, as time goes on! If you start with air, which is about 78% nitrogen and 21% oxygen, and the oxygen leaks out much faster than nitrogen, that means that when your tires lose a couple PSI, they've lost mostly oxygen, leaving a higher percentage of nitrogen in the tire. Let it go like that for a while and you might end up with 90% nitrogen anyway. So let the oxygen seep out naturally over time, and you've got nitrogen filled tires.

Thoughts?

Mike
 
#15 ·
Yea, problem is, for a tire to leak oxygen through it as a membrane, it would have to be as thin as a gum wrapper, which is 100,000 atoms thick, btw. Being that a tire is significantly thicker then a gum wrapper, no leakage will occur. :scatter:
 
#20 ·
Dry nitrogen and dry air will both expand and contract the same as temps change, nitrogen is no more "stable" than plain air. It's all about the moisture; It will cause large pressure changes as the temperature changes. In aircraft tires, this could mean a chunk of ice that causes the tire to come apart when it comes up to speed or it could mean a pressure spike and blow-out as the moisture goes from ice to vapor should the tires heat up high enough and quickly enough.

For race cars it's about pressure stability and predictability. Using dry nitrogen means they know what the pressure will be when the tires are up to temp. Not using a dry gas introduces an unknown quantity of moisture and that means tire pressures won't be predictable or even.

Technically, you could use dry oxygen and have the same results (watch out for open flames!) since it's also subject to the ideal gas law.

It's not about the gas, it's about the moisture. :)

Which makes this statement patently false.

-Adjust tire pressure for outside temperature. The tire pressure will rise 1 psi for every 12°F outside temperature with air and 1 psi for every 10°F with nitrogen. If you haven't adjusted the pressure since winter, your tires are over-pressurized.
It's 1psi for every 10F regardless of whether air or nitrogen is used.
 
#21 · (Edited)
Tiff of 5th Gear (UK TV show) did a test on this and while it's true Formula One cars use 100% pure nitrogen for their tires, he deduced it had no noticeable effect for, "Regular" car tires. I'll see if I can find it on YouTube and post it here.

Edit: Found it here's the vid: https://www.youtube.com/watch?v=kmnZ4-EUbIk
 
#22 ·
Here's a more scientific test exposing the myths of nitrogen vs air. :) I think I posted it before, not sure...

http://powertank.com/truth.or.hype/

EDIT: Yeah, it's on the first page of this thread.
 
#24 ·
The atomic masses of the two gases are different, which means when heated there are kinetic energy differences between the gasses. Nitrogen is lighter (with an atomic weight of 14.0067 vs oxygen with an atomic eight of 15.9994), and the molecules are larger (which also has its benefit when used in tires). The main benefit of nitrogen comes from the elimination of water vapor, which can turn into a gas and further change the tire pressure. These differences are extremely minuscule, and the numbers I published from outside sources may have larger variations than actual due to rounding differences. Maybe I'll pull out my old college Physics books and check the math later, but I have a fence to stain.
 
#25 · (Edited)
Lol... you guys from way down south arguing abut N2. You guys live in a very tempered climate and are looking at it in a fish bowl. It's a big world where some places in North America do see -40C to +35C temperature swings. Even places where you'll run on the highway at 50/80 mph for 3 to 6 hours at a time without stopping.

I deal with it, and work with it.. heck it's even part of my trade ticket. We even use it for testing piping systems that are sensitive to any moisture content like Hydrogen and Oxygen. Why? No moisture and not explosive or flammable. It displaces oxygen.

It also works great when testing systems that are half in the shade and half in the open. Pipes heat up in the sun and pressure falls. Same with tires.

N2 works great up here for tires in the great white north. You can't be adding and subtracting air all the time in the spring and fall when you have lots of temperature swings.

Do it... don't do it. It works, and it's stable. It's dry. Less prone to expansion and contraction from heat and cold....Fact. ..... So carry on your debates and articles.

If I lived in Texas or California... I probably wouldn't care about it as much either, but I don't. They also say changes of 2 to 3 psi in tire pressure can affect gas mileage and tire wear. Could be a reason it's done from the factory as well. Environmental reasons, otherwise, why would they bother? For ****'s and giggles??

If you don't like it or need it, don't use it. Saying that it's myth or snake oil is bias and not true in the real world. Run up around 130+ mph once in a while and have only 4 little rubber contact patches..... I'd like them stable please.... even if some think it's all in my head.

Been there, done that, bought the T-Shirt.
 
#26 ·
Lol... you guys from way down south arguing abut N2. You guys live in a very tempered climate and are looking at it in a fish bowl. It's a big world where some places in North America do see -40C to +35C temperature swings. Even places where you'll run on the highway at 50/80 mph for 3 to 6 hours at a time without stopping.

I deal with it, and work with it.. heck it's even part of my trade ticket. We even use it for testing piping systems that are sensitive to any moisture content like Hydrogen and Oxygen. Why? No moisture and not explosive or flammable. It displaces oxygen.

It also works great when testing systems that are half in the shade and half in the open. Pipes heat up in the sun and pressure falls. Same with tires.

N2 works great up here for tires in the great white north. You can't be adding and subtracting air all the time in the spring and fall when you have lots of temperature swings.

Do it... don't do it. It works, and it's stable. It's dry. Less prone to expansion and contraction from heat and cold....Fact. ..... So carry on your debates and articles.

If I lived in Texas or California... I probably wouldn't care about it as much either, but I don't. They also say changes of 2 to 3 psi in tire pressure can affect gas mileage and tire wear. Could be a reason it's done from the factory as well. Environmental reasons, otherwise, why would they bother? For ****'s and giggles??

If you don't like it or need it, don't use it. Saying that it's myth or snake oil is bias and not true in the real world. Run up around 130+ mph once in a while and have only 4 little rubber contact patches..... I'd like them stable please.... even if some think it's all in my head.

Been there, done that, bought the T-Shirt.
I'm not sure what you're arguing about. :confused: Dry nitrogen is more predictable because it's dry. In a sealed container the pressure will still go up and down depending on temperature. Using Nitrogen doesn't prevent pressure changes and it will do it just as much as dry air. Using nitrogen also doesn't stop you from having to adjust pressures for winter vs summer. Pressure will still drop in the cold and increase in the heat (Opposite of what you say above, which I've highlighted).

If using nitrogen is free then by all means use it, but unless I were a professional race car driver or pilot I wouldn't pay one cent to have it put into my tires no matter where I lived.
 
#37 ·
I got my tires filled with Nitrogen for free too, when i bought mine! they also threw in some oxygen and other trace gasses!
 
#32 ·
Are these posts for real.
 
#35 ·
Some good info here but bony crap, I use my AIR compressor from my garage about once a month after checking and go on my way.
 
#38 ·
Only way I would get Nitrogen in tires is if it was free, as it was the last time I bought tires over a year ago, they have 14k on them and have never been topped off and still have 34 PSI as when they were new, is that because of the nitrogen or just a good tire and seal? I thinks it's just a good set of tires and seal. I saw a sticker on a Challenger a few years ago and the dealer had installed Nitrogen and charged over $100 for it, that's insane!!!
 
#39 ·
Wow, didn't realize I was going to awaken sleeping dogs when I bumped this thread. Shoulda known better. ;) I've never for a second believed that nitrogen would have any noticeable effect on tires or performance. I just wanted to make the comment that the one myth about oxygen seeping out of the tire faster sorta shoots itself in the foot: if most of what leaks out is oxygen, what does that leave you with? Almost all nitrogen. So if that hypothesis/myth is true, who cares? Just pump your tires a few PSI above where they should be (with air) and only the oxygen will leak out, leaving you with almost all nitrogen in the tire. :)

Mike
 
#40 ·
I suspect that the entirety of the "nitrogen doesn't change pressure as much as air with temp" observation has to do with water vapor in the latter. Fill your tires with air on a real humid summer day, and when the temperature drops, some of the water condenses out, reducing the 'n' in PV = nRT.

Reduce n, and pressure falls. Starting at 100 degrees and 66% relative humidity, water will start condensing out at 86 degrees, and more and more will condense out as the temperature drops, reducing the partial pressure of H20, thereby reducing the overall pressure. This will be in addition to the drop in pressure from reducing the temp of the non-condensing gases.

So most of the effect of reduced pressure changes comes from lack of water vapor, not some magical property of 100% N2 vs 78% N2 20% O2. Truly dry air would work the same.

BTW, even the folks pushing Nitrogen inflation (the Get Nitrogen Institute) don't make claims to violate the Ideal Gas Law.
 
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#43 ·
Interesting. Trying to understand this... Isn't the water vapor that is in the air still H2O molecules? And won't it still be (the same number of) H2O molecules once it condenses? I thought condensation was just the clumping together of H2O molecules into a liquid. So I'm confused as to how they could take up less volume when the same molecules condense. Is it because of the molecular/lattice structure of the liquid taking up space when one H2O molecule is combined with others, i.e. more efficient piecing together of the molecules like a puzzle?

Mike
 
#42 ·
Or fill your tires in the dead of winter when the partial pressure of H2O will be very low. :icon_biggrin:

Seriously, though - I have no idea how well oil/water separators do at removing water vapor. Based on the dewpoint calculators I found online, if you're inflating when it's 90 degrees out, the air you're putting in has to have a RH of under 3% to prevent condensation down to 0 degrees F. That's REALLY dry.
 
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