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Discussion Starter · #1 ·
Guys- it's been a topic before, but I'd like to split some hairs...

There was a piece on a local TV station on this, citing improved tire life, increased safety and better performance- I disagreed and the reporter and I discussed it. My position is that the benefits are so minute that it really is immaterial - he cites reports (from vendors of nitrogen fill equipment) that purport specific benefits.

What is it?

Facts:

- Air is 78.4% Nitrogen
- The molecular weight of N2 is 28.02, O2 is 32... oxygen appears larger.
- All modern wheels are either alloy or painted.
- Air AND nitrogen is relatively dry, however technical grade ntrogen can be certified moisture free.

Let's assume that whatever is used, air (78%N) or notrogen that the tire pressure is properly maintained.

Is there an inherent benefit to Nitrogen fill?

I undertand that in truck fleets, where a tire may be re-treaded 4 times in 200k miles that internal oxidation may be a factor- is this a factor for single use passenger tires? (Heck mine are once a year, most are 2-3 years)

I do not beleive that diffusion of air and diffusion of nitrogen through the rubber affect the maintenance of pressure.

I do not beleive that nitrogen runs cooler.

I do not beleive that a tire, filled with air, is a fire danger given that it is surrounded by oxygen

Thoughts from you engineers and physics majors out there?

Anybody running N in the M5 for performance reasons?

A

PS Feel free to move this to Off topic if it needs to..


PPS The part that kills me? The video clip included interviews with Big O tire installers... the reporters said "Is this a good idea? We don't knw, but EVERY tire installer we spoke to runs it in their own tires." I guess that's good enough for anyone, eh?
 

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I was under the impression that nitrogen doesn't diffuse out of tires as quickly as oxygen. Therefore, tires filled with nitrogen will maintain pressure longer than tires just filled with air. Given how infrequenly most drivers check tire pressures, this is a good thing. I think as long as you maintain tire pressure, there won't be much benefit for using pure nitrogen. Also, if you have a home compressor with a water trap, you should be able to fill your tires with relatively dry air.
 

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Here is the deal. Nitrogen does not expand like Air does so you have a more constant tire pressure. Also when you fill with "air" you are introducing water into the tire which as we all know expands when heated.

If you have read any of Carrol Smiths books you can see a procedure for using nitrogen in the tires. You have to "remove" not bleed out all of the air in the tire prior to using nitrogen.

Jordan
 

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Discussion Starter · #4 ·
Olyar15 said:
I was under the impression that nitrogen doesn't diffuse out of tires as quickly as oxygen. Therefore, tires filled with nitrogen will maintain pressure longer than tires just filled with air. Given how infrequenly most drivers check tire pressures, this is a good thing. I think as long as you maintain tire pressure, there won't be much benefit for using pure nitrogen. Also, if you have a home compressor with a water trap, you should be able to fill your tires with relatively dry air.
I've heard that, but not from anyone that I'd trust...

Interestingly, Ingersoll Rand is selling nitrogen generators and hyping it up with press releases now that people are panicked over gas $$. A few outlets (like my local TV station) have picked this up and regurgitated the story.

But since I posted I found an excellent site, and a post on point:
http://www.eng-tips.com/viewthread.cfm?qid=120996&page=1

Should have searched first, huh?

Interesting comment by a chemical engineer that nitrogen actuall will duffuse FASTER than oxygen... since it is a smaller molecule...but even then some disgreement..

A
 

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Discussion Starter · #5 ·
jordantii said:
Here is the deal. Nitrogen does not expand like Air does so you have a more constant tire pressure. Also when you fill with "air" you are introducing water into the tire which as we all know expands when heated.

If you have read any of Carrol Smiths books you can see a procedure for using nitrogen in the tires. You have to "remove" not bleed out all of the air in the tire prior to using nitrogen.

Jordan
Read the link... it should be enlightening.
 

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We use nitrogen in Aircraft tires, and if its good enough for the navy I guess it should be good enough for my M5:)
 

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What up homes!!!

..most high end aircraft use it in the tires as its less flamable and during maximum braking and once you reach Brake energy limits, the temps of the brakes does not transfer as well. Also with the high alts that we fly, we dont have pressurized wheel wells and so any water would freeze as well as we would have huge swings in tire pressures.


this topic has actually been discussed a while back, I believe that memeber MIB brought it up. The problem with it, is that its quite expensvie (something like 100 for all four tires)
 

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Discussion Starter · #8 ·
Personally, I'm using Helium to reduce the unsprung weight...
 

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ard said:
Read the link... it should be enlightening.

I did Andy. And what I said holds true. My point was about moisture and pressure changes/swelling in the tire. In my race car I only use nitrogen and the pressure difference between hot and cold is much less than regular air.

Best,

Jordan
 

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Discussion Starter · #10 ·
OK, I can buy that the vapor pressure in air (or nitrogen) can impact PV relationships. What kind of temp differences do you see?

Thanks

Adam

PS Since I rarely sign posts, I'll answer to Andy as well .. :)
 

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I really see it as the law of diminishing returns in automotive applications. As ScKelleners said, it is importand in aviation, but cars do not see the extremes in environments that aircraft do. $100 for a N fill doesnt make too much sense to me.
I was cracking up Adam, as when I read that post I thought to myself "I could have sworn his name was Adam, and if not then I feel like an idiot for calling him that in the past." Good times.
:cheers:
 

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I think I would have typed this if I didn't read it first.

"When a tire heats up, the air and any moisture inside it heats up as well. When the moisture inside the tire heats up, the water molecules move further apart, increasing the tire pressure. By removing this moisture, the pressure stays more consistent over the entire heat cycle of the tire.

On a racecar, a 1/4 psi difference can change the handling of a car significantly. The humidity inside a tire does not have to be zero, but if it is not at least kept consistent from one set of tires to another, to equal a 1/4 psi increase in the current set, a 1 psi change may need to be made in another set because of the differing humidities."

I think the key word is "Consistent"
 

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I am so sorry Adam. I had a brain fart. It is not a temp thing but a pressure thing. At the track it is important. Normaly I would see my tires grow 8lbs with nitrogen maybe 3-4 pounds max and once they are set thats it. All done. Early morning or late in the day the tires remain consistent. You can get a small tank for not much money. It's the regulator that costs a bunch.

Jordan
 

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ard said:
Guys- it's been a topic before, but I'd like to split some hairs...

There was a piece on a local TV station on this, citing improved tire life, increased safety and better performance- I disagreed and the reporter and I discussed it. My position is that the benefits are so minute that it really is immaterial - he cites reports (from vendors of nitrogen fill equipment) that purport specific benefits.

What is it?

Facts:

- Air is 78.4% Nitrogen
- The molecular weight of N2 is 28.02, O2 is 32... oxygen appears larger.
- All modern wheels are either alloy or painted.
- Air AND nitrogen is relatively dry, however technical grade ntrogen can be certified moisture free.

Let's assume that whatever is used, air (78%N) or notrogen that the tire pressure is properly maintained.

Is there an inherent benefit to Nitrogen fill?

I undertand that in truck fleets, where a tire may be re-treaded 4 times in 200k miles that internal oxidation may be a factor- is this a factor for single use passenger tires? (Heck mine are once a year, most are 2-3 years)

I do not beleive that diffusion of air and diffusion of nitrogen through the rubber affect the maintenance of pressure.

I do not beleive that nitrogen runs cooler.

I do not beleive that a tire, filled with air, is a fire danger given that it is surrounded by oxygen

Thoughts from you engineers and physics majors out there?

Anybody running N in the M5 for performance reasons?

A

PS Feel free to move this to Off topic if it needs to..


PPS The part that kills me? The video clip included interviews with Big O tire installers... the reporters said "Is this a good idea? We don't knw, but EVERY tire installer we spoke to runs it in their own tires." I guess that's good enough for anyone, eh?
The compostion of dry air is quite uniform and is made up by volume of the following:
Nitrogen 78.084%
Oxygen 20.946%
Argon 0.934%
Carbon Dioxide 0.034%
The remaining components are known as rare gases and account for merely 0.003% of the atmosphere, neon, helium, krypton, hydrogen, xenon radon and carbon monoxide.

Yawwwwnnnnnn I know, my hobby is diving as a divemaster means that we have to teach this stuff in dive physics and trying to keep the students awake is difficult, but as soon as I mention that they can put nitrogen in their tyres they seem to be interested for some reason. Interestingly enough our bodies dont need the Nitrogen and somehow filters it out in our lungs, so why would our cars need it? Maybe cos it is a by-product that the companies need to get rid of?
WillM5AD
 

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A couple things. First, the smallest of points, more specifically, a clarification. It's been mentioned that our lungs filter out the nitrogen, rather, the nitrogen is the "carrier", and out lungs filter out the oxygen.

Next, I find it hard to believe that compressed air, presumably because it contains oxygen, is a fire hazard or at least promotes flammability. This seems unlikely, since the environment completely surrounding the compressed air is identically composed.

It's been said that perhaps a reason nitrogen is used in tires is because a compressed bottle (cylinder) of nitrogen is cheaper than air compressors. Well, if ecomomy was really the issue, then a compressed bottle of air would have been used. Air is readily available in cylinders as "dry air", "instrument air", "zero air" (no hydrocarbon impuritires), "breathing (medical) air", etc., etc. My point is that a cylinder of compressed air is probably cheaper than a cylinder of nitorgen, so if someone was trying to save money and/or make it convenient, they would use a cylinder of compressed air, not compressed nitrogen.

Now for a new idea. If you buy into this idea of exotic tire fillers, why stop at nitorgen? Argon is completely inert (non-reactive-Nitrogen is close, but not quite). It's atomic weight is 44 (if memory serves), so the permeability factor would be favorable for tire use. Argon is also readily available and relatively cheap as well.

Finally, some thought provocation. I seem to remember that Helium has a reverse coefficient of thermal expansion. So as the tire heats up, the pressure decreases. That would be wierd.

Who said science isn't fun?!
 

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ELEVENS said:
Next, I find it hard to believe that compressed air, presumably because it contains oxygen, is a fire hazard or at least promotes flammability. This seems unlikely, since the environment completely surrounding the compressed air is identically composed.

Now for a new idea. If you buy into this idea of exotic tire fillers, why stop at nitorgen? Argon is completely inert (non-reactive-Nitrogen is close, but not quite). It's atomic weight is 44 (if memory serves), so the permeability factor would be favorable for tire use. Argon is also readily available and relatively cheap as well.

Finally, some thought provocation. I seem to remember that Helium has a reverse coefficient of thermal expansion. So as the tire heats up, the pressure decreases. That would be wierd.

Who said science isn't fun?!
I'm new to the board and as a chemist, I admit, I have a pet peeve about nitrogen inflation (and the misinformation provided by the marketers).

The important factor for the conduction of fire is the concentration of oxygen in terms of mass (or grams) of oxygen per volume (liter). Percent composition does not change with increasing pressure. However, compressed air will have an increased oxygen concentration in terms of mass per volume. That being said there is insufficient heat generated in a automotive tire to intiate combustion.

If diffusion of gas through tire rubber is an issue, argon would be the way to go. Even if one fills with air and oxygen diffuses faster than nitrogen. Nitrogen would preferentially be concentrated by the tire and after several tire fill-ups a nitrogen rich atmosphere would be obtained anyway.

I think the coefficient of thermal expansion of helium is being confused with thermal conductivity. Helium has a very high thermal conductivity. Also, the speed of sound in helium is much quicker than that in air; this is the cause of a high voice while breathing from a helium balloon. Anyway, all gases, including oxygen, nitrogen, helium, argon and water, at the pressure and temperature inside a tire, would behave as ideal gases and expand at the same rate with temperature changes.

Also, as far as tire degradation from oxygen inside the tire. Tires degrade from the outside due to ozone (O3), not O2.

I'll save my rant about CSI for later.

Natdad
 

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Natdad said:
I'm new to the board and as a chemist, I admit, I have a pet peeve about nitrogen inflation (and the misinformation provided by the marketers).

The important factor for the conduction of fire is the concentration of oxygen in terms of mass (or grams) of oxygen per volume (liter). Percent composition does not change with increasing pressure. However, compressed air will have an increased oxygen concentration in terms of mass per volume. That being said there is insufficient heat generated in a automotive tire to intiate combustion.

If diffusion of gas through tire rubber is an issue, argon would be the way to go. Even if one fills with air and oxygen diffuses faster than nitrogen. Nitrogen would preferentially be concentrated by the tire and after several tire fill-ups a nitrogen rich atmosphere would be obtained anyway.

I think the coefficient of thermal expansion of helium is being confused with thermal conductivity. The high thermal conductivity of helium is the cause of a high voice while breathing from a helium balloon. All gases, including oxygen, nitrogen, helium, argon and water, at the pressure and temperature inside a tire, would behave as ideal gases and expand at the same rate with temperature changes.

Also, as far as tire degradation from oxygen inside the tire. Tires degrade from the outside due to ozone (O3), not O2.

I'll save my rant about CSI for later.

Natdad
Thank you for clarifying my rusty chemistry. It's been 20 years since I've practiced chemistry from the bench, they only let me push pencils around now and punch the keyboard ;)

Now, what's this about CSI? Not too bad, IMO. Not perfect, but at least the initial series was quite accurate. It steadily got worse though, as the show continued. "Bad" was the old TV show Quincy. Every show, it seemed, Quincy would take a sample into the lab and ask for a "complete breakdown" :rolleyes:
 

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Discussion Starter · #18 ·
Natdad- Welcome to the board! You share my pet peeve...

Will5ad- Did you read the story in Outside on ultradeep cave diving? 926 feet to be exact... chilling. worth a read.

Good posts, I'm enjoying the reads...

A
 

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One question on using nitrogen for tire inflation. How does one get all the oxygen and water vapor out of the tire to fill it with nitrogen?

IE, If you start with a normally inflated tire and let all the air out there is still 5-10 psi (0 psi would be a vacuum). This means that a good bit of O2 and water vapor still exist. So now you fill it with Nitrogen. You've reduced the percent of O2 but not eliminated it. Do you have to go thru several cycles to get to a higher percent of nitrogen?
 
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