Nitrogen vs C02

#1
This was brought up in another thread, and I have constantly heard things spewed all over the web about nitrogen being more stable than air or co2...


The Truths and Myths of nitrogen From Powertank.com

Lately there seems to be more and more hype about nitrogen gas for tires offered by tire companies and nitrogen services. Some services will "purge" your tires of air and replace it with near pure nitrogen for $20 per tire. Some tire shops are charging as much as $5 -10 per tire to fill them with nitrogen claiming everything from improved fuel mileage to a more comfortable ride. Is there any truth to this? Here we will take a close look at some facts and let you make up your own mind. At the bottom we show the results of our real-world gas comparison test that you might find interesting. In this article we refer to "gas" which includes air, nitrogen, and CO2.

Claim #1. "N2 doesn't expand with heat like air because it's drier so your tire pressures stay more constant through tire temperature changes." Here's a claim that we've heard more times than we';d like to admit. Bottled nitrogen is dry, drier than typical air, and it is said that a drier gas will exhibit less pressure change to temperature changes. This would mean that as my N2 filled tires heat up, the pressure will not go up as much as if they were filled with air. The dryness of CO2 is also put into question since it is a "liquid" gas under pressure. CO2 vapor is very dry. Don't forget that N2 is also a liquid gas under certain pressure and temperature. The truth is, the differences in thermal expansion values (TEV) between N2, air, and CO2 at automotive tire pressures is virtually undetectable to a driver. In our own tests we compared the pressure changes of N2, air, and CO2 through a wide temperature range and found that they all expanded (increased in pressure) at virtually the same rate (see Gas Test).

Claim #2. "N2 permeates (leaks) through tires slower than air therefore your tires will maintain their pressure longer and require less maintenance."
Although it is true that nitrogen does permeate through tire rubber slower than oxygen and CO2, there are two things to know. First, the gas permeation difference between oxygen, CO2 and nitrogen through a tire wall is very minute. Second, this difference is made even more insignificant for N2 since oxygen only makes up 17% of air and most of "air" (78%) is nitrogen. Diffusion speed through the walls of your tires has more to do with the quality, the wall thickness, and the age of your tires. More often, tire deflation is due to a leak in the stem core, the stem seal, cracks in the stem, a bad tire to wheel bead seal, cracks in the tire wall, or objects like nails stuck through the tire tread. Also, did you know that your tires may grow during the first 1-2 days as it gets used to being inflated which would reduce the tire pressure. Tire manufacturers recommend checking your tire pressures often no matter what type of gas you';re using to fill your tires. Bottom line: If gas permeation was the only way a tire would lose its "air" there would be very little detectable difference between air (which is already 80% nitrogen), nitrogen, and CO2.

Claim #3. "N2 is safer because it is non-combustible and therefore less likely that your tires will catch on fire."
This is true and is one reason aircraft tires are filled with nitrogen. But when was the last time your tires had to skid on pavement from 150 mph carrying 75 tons of vehicle, passenger and cargo weight? The chances are your tire is not going to burst into flames because of the additional 17% oxygen content inside your tires especially since your tires are surrounded by air anyway. If you have ever seen a tire smoking on the freeway chances are the tire was overheating from under-inflation. Putting nitrogen inside your tire will not prevent a tire from overheating. "But didn't I read that nitrogen will make my tires run cooler?" This statement is false. N2 cannot dissipate heat from a tire any faster than air or CO2 nor can it decrease heat producing friction between your tire tread and the road.

Claim #4. "N2 is safer for my tires because air contains oxygen and oxygen corrodes the inside of my tires."
Although it is true that oxygen permeating through the tire';s carcass may cause a certain level of oxidation, tire failures are typically not due to corrosion from the air inside. Don't forget, the outside of a tire is also exposed to oxygen not to mention harmful UV rays and ozone, the occasional curb bump, random road hazards, road salt and even dog urine. In fact, the leading cause of premature tire failure is tread separation caused by overheating; the overheating caused by friction from insufficient tire pressure. Premature tire failure is typically not caused by tire deterioration from the inside. CO2 vapor is dry and inert and also poses no corrosion issues to your tires. There is, however, one other possible cause for corrosion of tires that sit for long periods and that is moisture permeation from the ground. It is recommended that a moisture barrier (plastic sheet) be placed beneath each tire before long term outdoor storing.

Claim #5. "N2 is inert and therefore will not corrode the inside of my metal wheels."
This is TRUE, but who cares? Air won't corrode your wheels to the point of failure either, neither will CO2. Metal wheels Don't commonly fail due to corrosion from the inside of the rim. Wheels are well engineered parts of your car and for good reason. They support tons of moving weight over uneven terrain and obstacles. Have you ever heard of swapping out old wheels for new ones because the rims were made unsafe due to corrosion?

Claim #6. N2 in tires provides a smoother ride.
Yes, this is an actual claim in a nitrogen supplier's literature. Since nitrogen is no "softer" than air or CO2 our assumption for the claim is that if the nitrogen pressure doesn't increase as much as air the tires stay softer as the tire heats up. This is false (see Gas Test).

Claim #7. "N2 is used in aircraft tires and the NASA space shuttle tires so it must have advantages for me too."
Aircraft tire manuals state that oxygen content in the tires must not exceed 5%. This is to minimize combustibility. These tires also see extreme temperature and altitude swings that your car or RV tire will never experience.

Claim #8. "N2 in my tires will save me in fuel costs."
Fuel savings from tires depends on tire pressures. As long as tires are kept up to their proper pressures it does not matter which "gas" is in them. And no matter which gas you choose you should keep up a regular and frequent tire pressure check procedure because you never know when you may have picked up a nail or other tire damage that could be causing a leak.

Claim #9. N2 will make my tires last longer.
Tread longevity depends on tire pressure maintenance, alignment, and a properly working steering and suspension system. The only difference N2 makes in the interior of the tire is that there is no oxygen being diffused into the tire';s rubber. Interior carcass deterioration from an air filled tire is not an issue to be concerned about especially when compared to the affects of heat, UV, moisture, ozone, and road hazards that the tires are constantly exposed to.


The actual test they did is at this link.

http://www.powertank.com/truth.or.hype/
 
#2
Assuming thats a 40CF Tank which is around 6.5" diamter and 22" long



Lets say you want to air up from 10psi to 30psi:
P1V1=P2V2
(3000psi)(730in^3)=(20psi)V2
V2=109500 cubic inches at 30psi

A 35in tire has a volume of about 7703 cubic inches

109500/7703=14.2 tires.
 
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#3
Do co2 tanks contain more pressure? If not then why would a nitrogen tank not fill up as many tires as David was saying?

By gas laws as shown in your previous post it doesn't matter what gas is in there.
 
#4
Do co2 tanks contain more pressure? If not then why would a nitrogen tank not fill up as many tires as David was saying?

By gas laws as shown in your previous post it doesn't matter what gas is in there.
CO2 is stored as a liquid and as the liquid evaporates into the tank it holds the pressure constant until it is nearly empty. Nitrogen and compressed air, are stored as a gas.
 
#5
To expand on that, CO2 holds a relatively constant pressure of 700psi till nearly empty (this is why the visual pressure gauges on CO2 and propane are kind funny, because they only show that the pressure is dropping when you are dam near empty. where as the nitrogen will be at a max of 3000 psi when you fill it down to 0psi as you use it.
 
#6
Where are you gona get that co2 tank filled at and at what cost. The LWS usually only does tank exchange. I have filled my shocks and tires many time with my N2 tank and I'm still sittin at 1400 psi. No way in hell your gona sell me on that co2 . that shi holds moisture and N2 doesn't.
 
#7
Where are you gona get that co2 tank filled at and at what cost. The LWS usually only does tank exchange. I have filled my shocks and tires many time with my N2 tank and I'm still sittin at 1400 psi. No way in hell your gona sell me on that co2 . that shi holds moisture and N2 doesn't.
If its a cheap steel tank why not just swap it out? The local welding shop does do fills though, as does the welding shop near clemson where Mason is. Anyplace that fills or exchanges Nitrogen should be able to do the same with CO2.

Personally, I'm not trying to sell anyone on CO2, this is just some facts and friendly discussion.
 
#8
Where are you gona get that co2 tank filled at and at what cost. The LWS usually only does tank exchange. I have filled my shocks and tires many time with my N2 tank and I'm still sittin at 1400 psi. No way in hell your gona sell me on that co2 . that shi holds moisture and N2 doesn't.
I just caught the moisture comment, The moisture is a non issue because more moisture is already in the tire/wheel assembly just from the residual mounting lubricant that gets inside during the mounting process, let alone mounting them on a humid day -- nobody pulls a vacuum on a tire (as though it would be possible) or bakes it out before putting in the nitrogen.
 
#9
Nitrogen is great for racing due to claim #1. Since it doesn't expand as much under heat, the tire pressure will be lower. I've seen nitrogen tires be almost 10 psi less than those filled with air coming off the track. The cars would start off at 30 psi, then expand to 37~39 psi. Cars with air sometimes would expand to nearly 50 psi. Yeah, traction would be significantly reduced and the cars with air in their tires would be skidding around or would be sluggish with underinflated tires at the start.

HOWEVER, this is for cars...on road atlanta...doing 120 mph and faster. If this is your application, then nitrogen is the way to go. However considering the average speed of a 4WD in low range, I do not consider this to be the case.

Unless you are Kirby, doing 70 mph in low range or whatever it was.

Lastly I kinda invested in an air compressor for the garage and C02 for the trail so I'm kinda committed. I've toyed with the idea of getting a kickin' air compressor but the C02 tank works.
 
#10
Nitrogen is great for racing due to claim #1. Since it doesn't expand as much under heat, the tire pressure will be lower. I've seen nitrogen tires be almost 10 psi less than those filled with air coming off the track. The cars would start off at 30 psi, then expand to 37~39 psi. Cars with air sometimes would expand to nearly 50 psi. Yeah, traction would be significantly reduced and the cars with air in their tires would be skidding around or would be sluggish with underinflated tires at the start.

HOWEVER, this is for cars...on road atlanta...doing 120 mph and faster. If this is your application, then nitrogen is the way to go. However considering the average speed of a 4WD in low range, I do not consider this to be the case.

Unless you are Kirby, doing 70 mph in low range or whatever it was.

Lastly I kinda invested in an air compressor for the garage and C02 for the trail so I'm kinda committed. I've toyed with the idea of getting a kickin' air compressor but the C02 tank works.
did you read this? I find this pretty straight forward that the temp differences don't affect the pressure differently from CO2 to N2 to Compressed Air

check out the bottom with the pics:

http://www.powertank.com/truth.or.hype/
 
#11
seems that the moisture is what allows the greater temperature change in racing applications not the Nitrogen vs Air. Having your tires flushed with nitrogen can eliminate many of the contaminants found in regular compressed air which will help with the pressure changes. But unless you are in a racing application I dont think you are going to notice the difference, as max said.
 
#12
did you read this? I find this pretty straight forward that the temp differences don't affect the pressure differently from CO2 to N2 to Compressed Air

check out the bottom with the pics:

http://www.powertank.com/truth.or.hype/
Using power tanks website for info regarding the subject may be a bit one sided. Not saying that their info isn't quotable by any means, I'm just saying that they definitely won't be putting up more pros of nitrogen than co2 if they are trying to sell you a bottle of co2.


But from what I've gotten so far is that either will work. But nitrogen has a much smaller edge on co2 than its repped up to have.
 
#13
Using power tanks website for info regarding the subject may be a bit one sided. Not saying that their info isn't quotable by any means, I'm just saying that they definitely won't be putting up more pros of nitrogen than co2 if they are trying to sell you a bottle of co2.


But from what I've gotten so far is that either will work. But nitrogen has a much smaller edge on co2 than its repped up to have.
Powertank also sells nitrogen setups.

and I would say the edge is in performance once installed, the CO2 still has the edge of being able to transport more gas per container.
 
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#14
Conclusion of High Pressure Gas Test:
At the higher tire pressure commonly seen in RV tires we took the gases through a temperature range of 154ºF (-20ºF up to 134ºF). Our start pressure was 80 PSI @ -20ºF and over the 154ºF temperature increase we saw the gas pressures all increase virtually the same amount to within 2 PSI of each other. In the end, the N2 and "air" test samples topped at 108 PSI while the CO2 sample topped out at 110 PSI. Note that the pressure changes that we saw in our bottles are the same as what you'd experience in your big RV tires despite the difference in volume. What does this mean? No matter which of these gases is in your RV tires, your handling, performance and tire wear will be the same.

THE IDEAL GAS LAW FORMULA might help explain why different gases expand at virtually the same rate as their temperature increases.
A gas may be completely described by its makeup, pressure, temperature, and volume. Where P is the pressure, V is the volume, n is the number of mols of gas, T is the absolute temperature, and R is the Universal Gas Constant,

PV=nRT

This formula is the "Ideal Gas Law Formula." Although there is no such thing as an ideal gas the formula is pretty accurate for N2, CO2, and oxygen as we assume that the gas molecules are point masses and the collisions of the molecules are totally elastic. (A completely elastic collision means that the energy of the molecules before a collision equals the energy of the molecules after a collision, or, to put it another way, there is no attraction among the molecules.) The formula becomes less accurate as the gas becomes very compressed and as the temperature decreases but here "very compressed" pressures are well above even the highest tire pressures and "decreased temperatures" are extremely cold, too cold for tires. There are some correction factors for both of these factors for each gas to convert it to a Real Gas Law Formula, but the Ideal Gas Law is a good estimation of the way N2, CO2 and "air" should react through temperature changes. What does all this mean? It simply means that "air", nitrogen vapor, and CO2 vapor should all react pretty much the same within normal tire pressures (0-120 PSI) and temperatures.
 
#15
I just caught the moisture comment, The moisture is a non issue because more moisture is already in the tire/wheel assembly just from the residual mounting lubricant that gets inside during the mounting process, let alone mounting them on a humid day -- nobody pulls a vacuum on a tire (as though it would be possible) or bakes it out before putting in the nitrogen.
The reason I'm so stuck on 'n2 is because I use it for my shocks. So moisture is an issue for me. But that's just me.
 
#17
Which gas you use is really not going to make much of a difference with our big heavy tires as said before.

The CO2 hands down has the edge on capacity though. I'll get 4-5 times the use out of my 20# CO2 tank to a similar size nitrogen tank that costs roughly the same to fill. Also the CO2 comes out dry, way dryer than my compressor air.

The reason I'm so stuck on 'n2 is because I use it for my shocks. So moisture is an issue for me. But that's just me.
In this case you have to have the N2 for the shocks, but I think I would just keep a small cylinder for shocks, and use CO2 for everything else. Most people aren't rebuilding and tuning there shocks that often.
 
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#18
When I worked at the Nissan dealership we sold the n2 exchange service or whatever they called it but in all honesty I always though of it as a rip off seeing as just plain ole air is like 70% n2 I never really saw it as being a major advantage unless like previously stated your doing 120mph at the track all day or putting it in shocks
 
#19
Nitrogen for me but only because I have unlimited supply at work and can transfill it myself. All for the big cost of zero dollars bitches.
 
#20
Seeing this thread makes me remember I should fill the CO2 tank I got from Brooks 3-4 years ago and put it in my truck/trailer/buggy.....somewhere and keep it handy.
 
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