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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.
 

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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.
 

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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
 

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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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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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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....
 

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Carefully drain the Nitrogen and refill the tires with Helium. The car will pick up 0.02 in the quarter mile!
 

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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.
The only thing that N2 gives you is a dry (as in as close to 0 RH as you can get) fill of gas. All gasses will expand and contract due to temperature. Boyle's Law. The water vapor in ambient air will condense out al lower temps and cause greater fluctuations in the tire pressure. Also O2 will react or migrate through the rubber over time. N2 tends to stay put,

N2 and room air both have to obey Boyle's Law.
 

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The only thing that N2 gives you is a dry (as in as close to 0 RH as you can get) fill of gas. All gasses will expand and contract due to temperature. Boyle's Law. The water vapor in ambient air will condense out al lower temps and cause greater fluctuations in the tire pressure. Also O2 will react or migrate through the rubber over time. N2 tends to stay put,

N2 and room air both have to obey Boyle's Law.
Ideal gas law. ;) Boyle's law is pressure in relation to volume, not temperature.
 

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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
 

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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

Just another snake oil to relieve you of your $$$$, plenty out there.
 

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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:
 

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You guys are all wrong! I fill my tires up with hot buttery maple syrup. Let me tell you, when I burn out at a green light, all anyone is thinking about is waffles!
 

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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%


.,
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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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.
 
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