Tires - Nitrogen versus Air

[DOCTORBILL]

JustSayGo got me interested in Nitrogen versus Air for inflating one's tires.

I have always considered the whole thing as a gimmick....

COSTCO's brochure says Oxygen in Air escapes 3 to 4 times faster then Nitrogen
since Oxygen Molecules are smaller than Nitrogen Molecules.

I looked it up - Oxygen Molecules are about 95% of the size of Nitrogen Molecules.

A difference of 5%....yet they say this makes for 3 to 4 times faster....doubt is in my mind.

I need Literature references of scientific research done by Chemists, Physicists and Engineers.

It seems like it is quite hard to disconnect those selling this concept from
anyone doing research on unequivically proving the concept....

Here are web links on this subject that I found by Googling:

http://ezinearticles.com/?Selling-Ni...-Air?&id=38142

Nitrogen at $10 per tire!?
http://www.sptimes.com/2005/09/28/Ta...our_tire.shtml

Nitrogen in BIG cylinders is rather cheap! Charging over $1 / tire would be
criminal, in my humble opinion.....

http://www.cartalk.com/content/colum...tember/05.html

Here the Environmental 'Simple Minds' have a hold of it...Lord!
http://www.treehugger.com/files/2005...te_your_ti.php

A comment on this subject
http://fightingforscience.com/category/physics/

http://www.bargaineering.com/article...s-mileage.html

Here is a discussion group on this topic....
http://www.eng-tips.com/viewthread.c...=120996&page=1

This was cut and pasted from the bottom of the following page:
http://www.ces.clemson.edu/ssnems/in...s/page0002.htm

"Automotive Systems

· Tire Nitrogen Filling System

The rolling resistance of inflated tires is an important component of resistance to vehicle motion and contributes to the total load and fuel consumption. Therefore, many research works have been focused on how the various tire parameters (e.g., load, inflation pressure, speed) affect rolling resistance so that fuel economy can be increased. Recent research findings indicate that filling tire with nitrogen can maintain proper inflation and decrease the deterioration of the rubber. Therefore, the primary objective of this project is to concentrate on effects of theses parameters on rolling resistance and especially nitrogen inflation to increase vehicle safety, performance and operating cost.

The rolling resistance (RR) is essentially a moment, however, active force is needed to move the wheel forward. As a result, this force acts in the travel direction at the axle of a towed wheel and at the perimeter of a driving wheel. RR is caused by tire deformation, which results in normal force to be shifted forward causing a torque around the wheel center that resists rolling.

Since the RR is proportional to normal force, it is natural to define the coefficient of rolling resistance Cr as:

Fr = (Cr)(N)

where Cr depends on many variables such as inflation pressure, tire temperature, vehicle speed and wheel adjustments.

Previous research works show that dry nitrogen can maintain the proper tire inflation pressure to make tires run cooler, which can decrease the RR and prevent overload. A 30% increase in RR can increases fuel consumption by 3-5% depending on driving conditions and vehicle type.

A new parameter MERFU/H defined to compare the rolling resistance of different tires under various driving conditions, which is the mean equivalent rolling force over any standard urban (U) or highway (H) cycle. to is time corresponding to the start of the cycle, with tf being the end of the cycle.

The project is aimed at the development of an analytical/numerical method using correlation and spectral analyses to be utilized for RR identification. To achieve the objectives of the project, a variety of current production tires tested under the auspices of SAE J2452, account for various conditions of speed, load and inflation pressure. During this task both nitrogen and air inflated tires will be tested at Michelin America Research and Development (MARC) and the parameters MERF and SMERF (Standard Mean Equivalent Rolling Force) will be calculated to compare tires for driving cycle combination based on test data provided by MARC. Using available statistical toolboxes (e.g., Matlab), the experimental data provided by MARC will be analyzed to predict the tire performance during its whole lifetime based on the tire modeling. The rolling resistance values predicted using this model will be compared with the rolling resistance coefficients measured during the SAE proposed test. Compared to air, dry nitrogen is expected to maintain better inflation pressure, which can decrease the rolling resistance and prevent overload."
end quote

Is it just me, or is this hard to read? Not well written....

I'd like to see where this is going to be published....

DoctorBill

[mainemetro]

People, listen up. It is a scam!

#1 - Your tire is NOT going to rot out from the inside - it is going to wear out from the outside - period.

#2 - A gas is a gas is a gas...PV=nRT ....unless you are cooling a gas to the point of condensation, or compressing it to hundreds of atmospheres pressure, it changes pressure according to the Ideal Gas Law equation: Pressure X Volume = number of moles of gas X gas constant X Temperature. Notice that the TYPE of gas is NOT in this equation at all. That is because IT DOESN'T MATTER. Nitogen, oxygen, CO2, argon, whatever - they are ALL THE SAME. This is an absolute proven fact, a scientific Law.

#3 - Nitrogen and oxygen diffusion rates through a tire are not significantly different whereas the two molecules, N2 and O2 are very similar in molecular size and mass. Even if O2 diffused through the tire more quickly this would only serve to concentrate N2 in the tire and you would eventually end up with a nitogen-filled tire over time and re-inflation with air.

#4 - Notice that some gases that are NOT recommended to fill tires with:
Hydrogen - diffuses rapidly through tire, and is explosively flammable
Steam (water vapor) - condenses to a liquid at temperatures below 212F and then tires go flat
Nerve Gas - tough on the "tire service technician" when fixing a leak



ps - congratulations to you, Doc, for raising the Phoenix!

Mainemetro

[99Metro]

Well, Nascar tires are filled with Nitrogen, and I believe it helps keep the tires cool. I don't think there would be any difference in what you used to fill the tires (air versus nitrogen), unless you were doing serious track races where tire cooling would affect performance. I think that if I substituted air for nitrogen in MY tires, I would still have that same slow leak in the driver's rear...! Molecule size does make a difference in certain things that require it, but I don't think it would with tires. Although nitrogen is relatively cheap, air is cheaper.

[DOCTORBILL]

I got to thinking about this Nitrogen in tires business AGAIN - saw the sign at COSTCO.

Nitrogen is supposedly better than Air because the N2 molecule is non-oxidizing as is O2.

Blah, blah, blah.

HOWEVER - if anyone argues N2 over O2 due to molecular size, then why not
use Carbon Dioxide?

CO2 is one of the cheapest gases and is almost 1.5x the molecular weight of O2
and the molecule is linear.

O2 is 32. N2 is 28 CO2 is 44 AMU.

CO2 is also non-oxidizing like N2.

You can get CO2 filled into thermos bottle sized cylinders used for PaintBall guns....cheap!

DoctorBill

[TENGRAM]

as was mentioned this has been used in nascar for a long time, and also in formula 1, indy, le mans, and aerospace. it seems that engineers all agree that it is better and for me this is enough to convince me... but i do like to know why this is.

here's a couple of points i have to offer:

from http://www.layover.com/news/article/...ense-8634.html - "Among the benefits of nitrogen inflation: less inflation pressure loss for a more stable, consistent tire pressure; cooler running tires; longer tread life; less oxidation of tire components, and reduced rim and wheel corrosion. The result is increased tire life, improved fuel economy, reduced tire aging and a more durable casing for improved retreadability."

and, i hesitate to use this source but in this case it seems very accurate...http://en.wikipedia.org/wiki/Ideal_gas_law - "The ideal gas law is most accurate for monoatomic gases at high temperatures and low pressures. This follows because it neglects both molecular size and intermolecular attractions. Obviously the neglect of molecular size becomes less important for larger volumes, i.e., for lower pressures." "The more-accurate van der Waals equation takes into consideration both molecular size and attraction."


great discussion BTW opcorn:

[DOCTORBILL]

A great deal of what passes for "evidence" is opinion...

Being in 'science', I am VERY sceptical of words like "..engineers all agree that it is better..."

Doctors tell you to drink 8 glasses of water a day, but NOWHERE in the Literature
(where actual experimentally derived data is published) can anyone find any
data to support that admonition!

Can any of those 'engineers' (by the way - any names?) cite research evidence
to support "...less inflation pressure loss for a more stable, consistent tire pressure;
cooler running tires; longer tread life; less oxidation of tire components, and
reduced rim and wheel corrosion."

All I am asking for is some sort of published PROOF and not assumptions and conjecture.
Something published in a reputable journal - not "Popular Science" Magazine....

So much so called science is opinion given by some authority who started it and
the opinion somehow gets changed into a 'law' or into 'scientific evidence supports....'
when NOTHING supports the concept !

I am not trying to be an A**hole, I'm just asking for proof !

To prove something, one needs to run EXPERIMENTS involving controls
with and without the variable, done enough times to rule out flukes and
better done double blind to rule out personal beliefs of the people involved
from influencing the 'outcomes'.

Probably 20 city busses, 10 with - 10 without N2 (only a couple maintenance
people know which) run for 5 years with some written protocol followed
scrupulously to examine the used tires very carefully and thoroughly
would yield some good data.

I suppose this topic is not of enough monetary interest to cause anyone to
carry out expensive experiments.

Tire companies would be the best group to do this, but I suspect they like to
see more tire wear ocurring than not.

DoctorBill

[TENGRAM]

Originally Posted by DOCTORBILL

A great deal of what passes for "evidence" is opinion...

Being in 'science', I am VERY sceptical of words like "..engineers all agree that it is better..."
...Can any of those 'engineers' (by the way - any names?) cite research evidence
to support "...less inflation pressure loss for a more stable, consistent tire pressure;
cooler running tires; longer tread life; less oxidation of tire components, and
reduced rim and wheel corrosion."

my point is, no specific engineer's name is needed. engineers in the top fields seem to agree on this subject. its not by accident and not based off of opinion or some old wives tale. they have a much more extensive knowledge base than me so i can only assume they know whats right. like i said though, i would like to know why, but until i do i rest assured that there is valid evidence of it. maybe you could plug some data into the van der waals eqn and find out what is really happening? try different pressures and temperatures for both air (~80% n2, ~20% o2) and n2. see which one changes the least given different environments.

[DOCTORBILL]

TENGRAM - I am not attacking you when I say this....

I reiterate - where's the Beef ?

Where is the data that these anonymous "Engineers" are relying on to advocate N2 in tires?

"...they have a much more extensive knowledge base..." - if so, where is it published?

Goofy stuff gets reinforced by the use of such language until it becomes the 'truth.'

If a majority of voters think George Bush is doing the right thing - is he?

If a Learned Political Expert with a PhD from MIT says George or Hillary are right - are they?

Same for Medical doctors 20 years ago saying that bacteria being the cause
of stomach ulcers is Bullcrap! No bacteria can live at pH 1....!

There was a time that saying that made the Doctors (physiological engineers) throw rotton tomatoes
at you at Medical meetings.

I had arguments with our Corporate Medical Doctor over that.

Well, it is now shown by published research data that bacteria (that live in stomach acid at pH 1)
do cause most all ulcers. See end of this posting.

Now it is accepted fact.

Believing what engineers, physicists, chemists, evangelical TV hosts, and bartenders
say they believe without them showing you the DATA will often make you look silly.

In science, there are many, many opinions about what is happening chemically or
physically with various things.

Little is actually proven.

Folks get mad and put out when I continue to ask - where is the data?

If N2 is so damned good for tires - where is ANY DATA to substantiate that ?

Show me. If there is data - it shouldn't be hard to show it to me....

And if you find something, is it DATA or opinion continually reiterated ?

Where are the numbers, the measurements, the scientists names, the lab location, the
date it was done, the journal it was published in ? Who paid for the research ?

Look for the words "in the opinion of" and "experts say" and you can probably be
certain that they are selling you something.

Like those "Doctors" on TV ads for winkie enlarging pills.... ya, right.

Where is the data and who did the experiments ?

You just wait folks - you'll see a lot of this sort of thing about Global Warming soon.

The experts say.....

Scientists agree......

It is common knowledge that....

Any moron knows.... (implications that if you oppose it, you are a moron).

An awful lot of what is called science is baloney used to sell goods or political action.

Are some of you who are reading this getting angry?

Why?

DoctorBill

http://healthlink.mcw.edu/article/956711536.html
All of this has a 'paper trail' of PUBLICATIONS to prove it via experimental DATA.
i.e. - The Beef...

[TENGRAM]

i agree with you on many points here, and i don't portend that i know for fact that N2 is superior for tire inflation. the truth is, little in this world can be proven at all. not to start with the philosophy BS, but anything you KNOW for a fact can be disputed as being an actual fact even if you experience it first hand.

that said, there are two things you can do to prove with 99% certainty that N2 is better. research (but somewhere down the line you will have to take someones word on something), or experiment (which is inherently subject to many sources of error). a simple experiment (although consequently less accurate) would be to inflate several balloons, half of them with N2 and the other half with "regular" air. over time i would bet that the air baloons will have lost more pressure. these of course aren't exactly the same conditions as a tire but i think it will be enough to provide a reasonable degree of certainty. or you could bite the bullet and air your tires up with N2 (carefully evacuating all of the air first). maybe just air one front tire up with N2 and the other with plain air. check the pressure periodically for a few months.

i'm sure there is data out there that can "prove" the N2 theory and i'm surprised we can't find it. i'll do some searching later this week when i have time. but like i said, you will have to take someones word for it somewhere down the line, or else test it yourself.

opcorn:

[TENGRAM]

http://blogs.consumerreports.org/car...nitrogen-.html



if the pic doesn't show up it can be found through the link i posted.


i'll find more later

[DOCTORBILL]

As my old father used to say, "Now you're cooking with gas!"

NOW you have something to talk about!

Very interesting Consumer reports article which I would 'tend' to believe seeing
that they have no "ax to grind", as it were.

However, I love the comments at the end of the CR article !

So you lose a tad less pressure over time! That causes folks to be less diligent
about watching the tire pressure! You still lose pressure - just not as quickly...

I'd bet the higher loss with AIR is the O2 reacting with the rubber! Oxidation.

Now - back to CO2 ! Much less expensive! Unreactive like N2.

Go buy a PAINTBALL cylinder ($25) and set up a CO2 filling device and maintain
PSI's with CO2.....

CO2 is 1.5 times larger a molecule than N2.... should pass thru the rubber much
slower - sounds good, huh?

See! "Sounds good" - must be true!

Maybe I'll start some 'Blog' about the virtues of CO2 and maybe I can start a
new FAD and become famous!

I have a PhD in Chemistry (UC Davis 1973), so I am an "expert" and everyone
should believe me!

Lord God.....lol

Anyway - I am happy.

I stirred the pot and now folks are THINKING.

Keep looking for scientific data.

I loved the line in the CR Article.

I quote, "The use of nitrogen in large truck fleets and the commercial tire industry
are well documented and support these claims."

Do you see how stuff gets passed on and built up w/o any data?

It supports the claims! Holy Makeral!

I worked in industry....the CEO makes some dufus decision and orders something
be done....POWER !

Corporations contribute to political parties! They contribute to bogus environmental stuff !
On the orders of the current CEO....! many CEO's are very strange people.

Again - where is the Beef ?

I for one will just go to my garage, fire up my air compressor and fill the tires
as needed....with air (free until the Feds start taxing it)

Better mileage (1 mpg better, 3-5 mpg better..) HA !

I liked the comment - is this the Placebo effect?

I discussed how 2/10th of a gallon variation on fill-up can change one's mpg calculations
by several percent!

mpg measurements are so filled with error as to be laughable! How many fillups done for those
mpg improvements? One?

Did they fill the tank to what - overflowing. How did they accurately measure
the gallons filled?

Piffle.

This is a tempest in a teapot. A mountain into a molehill (or vice versa)...

However - this is fun to discuss. Be a good topic when half tight on 5 beers!

I can see guys getting into heavy arguments over this at an afternoon BBQ get-together!

Nice thread - lots of fun.....no beer though.

See how minutia can turn into heated discussion.

Maybe I can write to Hillary and when she is in power she can force a Federal Law
thru Congress that we all HAVE TO use N2 to save the environment!

The Nitrogen Police will break into your house a 3 AM and arrest you scofflaws who
use air in your tires. Drag you away to "tire prison camps" for 'rehabilitation'.

Another idea! Fill the tires with BUTANE ! C4H10. Huge gas molecule compared to N2.
That's the gas in Butane Lighters.

Sorry - I'm in some screwie mood right now. Been listening to Michael Savage ranting
on the radio about how screwed up we all are in America.

DoctorBill - the Metroglodite.

[brivers]

I use propane in my tires. Its great for tailgating when you don't have room for that nasty tank.

[TENGRAM]

i remembered a thread on http://www.corner-carvers.com/ that discussed nitrogen so i revisited it. some of the interesting things said:

Originally Posted by Bart Carter

At WSIR a couple of weekends ago the track tire shop filled a flat I had with compressed air. I run nitrogen, so I took it back to the trailer to purge the air. I usually do 3 full purges and that seems to work well.

When I did the first purge, I got so much water my hand was completely soaked. Same with the second purge. With the third purge, I finally got very little water, just a dampness. It's the water that causes most of the pressure difference.

and Doc, you may be too late on the CO2 idea:

Originally Posted by TeamDFL

Does carbon dioxide offer some of the benfits of nitrogen? CO2 seems to be popular with the off road types due to availability and cost. A tank of CO2 would be "dry" just like nitrogen. According to the miniscule amount of info I retained from Chem105/106, dry CO2, like dry N2, would behave like an ideal gas (PV=NRT)

http://www.wheelersoffroad.com/co2systems.htm


.

[Woodie83]

The reason Nitrogen is used in racing tires is because it is more predictable in the way the pressure increases with temperature. The Oxygen in air allows it to carry water (humidity) and the water vapor expands much more than gas does, either Nitrogen, Oxygen, Air, anything. Most racing tires operate around 200 degrees, close to boiling. It's not easy to tell how much water vapor is in there, so you can't tell what's going to happen to pressure at those temperatures. The top teams adjust handling by changing the pressure of a single tire by a quarter of a PSI, if it happens to be more humid at the time they adjust it than it was when they originally filled the tires, they don't even know what the final effect will be. Nitrogen eliminates this factor completely.

As used at tire shops for street use, it's just a scam. It does leak out through the pores in the tire less, but if you need to measure it for a year to see an appreciable difference, who cares? The difference between summer and winter is far greater than that.

[DOCTORBILL]

Any gas follows the Ideal Gas Laws - close to 100%.

Water vapor is a gas until the humidity reaches 100% capacity for the temperature
the air is at and then it starts condensing.

PV = nRT where n = amount of gas (in moles) and R = the gas constant

T = temperature in degrees Kelvin (Absolute 32°F = 273 Kelvin degrees)

If there is a small amount of humidity in the Tire air, it will take up the same
space as any other gas.

If a lot of water is in the tire, the water vapor will condense when 100%
humidity is achieved for that temperature.

As the tire warms up, the water will re-vaporize to the gas phase.

No tire should have liquid water in it unless the air compressor used to fill the tire
had liquid in the lines and is squirting water out the hose!

I've never seen any air line do that....any water should collect in the BOTTOM
of the compresor tank - not go out the hose!

Any water inside the tire should not pose a problem unless it is in the liquid
phase when it can cause corrosion of the wheel metal due to electrical oxidation/reduction
reactions with oxygen in the air (20%).

If water were in a Nitrogen filled tire, corrosion would be negligible (wheels).

DoctorBill