Are Nitrogen Filled Tires A Gimmick?

[David Pratt]

Replacing the Air in the tires with Nitrogen was a topic that was heavily discussed in Chuck Thatchers TYRON BAND Seminar. I found this article in a National Publication and thought it might be beneficial to those members interested in the pro's and cons of using Nitrogen.

I personally use Nitrogen in the tires of every vehicle I own including my Foretravel Motor Coach, Collector/Classic Automobiles, Aircraft and anything else that has a tire on it.

I thought that was a very good article and should be shared with all the members and shed some light on any gray areas about the use of Nitrogen in tires.

I am sure that there are those that do not share what this information is about. Your comments are welcome, but play nice.

The Difference Between Nitrogen And Air

Nitrogen and air are two of the most common gasses to fill inflatable tires. Nitrogen molecules are larger than air molecules, making it harder to leak over time. With air in your tires, you may lose pressure in your tires and need to top them off more often.

Nitrogen is also a dry gas, which does not support moisture. Moisture can cause the rubber compounds in tires to break down and cause premature aging for your tires. Using air can allow moisture to enter your tires and cause internal corrosion to the metal beads, steel plies and wheels on your vehicle.

No matter which type of gas you put in your tires, you should check your tire pressure regularly. Driving with underinflated tires can be dangerous no matter what type of gas is inside of them. 

Proposed Benefits Of Using Nitrogen Over Air In Tires

Using nitrogen over air in your tires can be very beneficial. Let’s look at a handful of the reasons why you might consider using nitrogen in your tires.

Reduce Air Loss

All tires experience a loss of pressure, but the type of gas used can reduce this loss.  Consumer Reports shares that a tire with regular air will typically lose about 1 or 2 PSI of air pressure per month. On the other hand, nitrogen tires lose about 1 or 3 PSI over an entire year.

Nitrogen contains larger molecules. Punctures from nails and other road hazards will still damage your nitrogen-filled tires and cause pressure loss. However, you’re less likely to experience changes in pressure under normal driving circumstances.

Improve Fuel Economy

Because nitrogen tires are less likely to lose pressure, it helps ensure proper inflation. Having your tires properly inflated is essential for optimal fuel efficiency. Driving on under-inflated tires reduces your fuel economy. 

Tire sales giant Les Schwab states that for every 1 PSI drop in pressure for a tire, drivers can experience a 0.2% decrease in fuel efficiency. With the rising cost of fuel recently, keeping your tires properly inflated can result in massive savings each year.

Increase Safety

Driving with underinflated tires is incredibly dangerous. When a tire is low on pressure, more of the tire comes in contact with the road. This increases the amount of friction between the tire and the road. Friction generates heat, which causes the rubber compounds to break down. This can drastically increase the wear and tear on your tires and reduce the life of your tires.

You’re more likely to experience a tire failure or blow out on an aging tire. A blowout while you’re traveling 65 mph down the highway, can be extremely hazardous. It can cause you to lose control of your Motor Home and potentially cause an accident.

Keeping your tires at the proper pressure keeps you and others on the road safe.

Maintaining Tire Pressure

You want to maintain the proper tire pressure for your tires. Nitrogen-filled tires can maintain tire pressure even when not driven regularly. You’ll still experience some pressure loss over an extended time, but it is drastically less than a tire filled with air.

While you should still keep an eye on your tire pressure, nitrogen tires don’t require nearly as much constant attention as tires with air.

Do Nitrogen Filled Tires Really Work?

YES, nitrogen-filled tires do work better than air tires. They perform better and help ensure your tires stay properly inflated. Research indicates that nitrogen tires are 74% more effective at maintaining proper tire pressure over tires filled with air.

There once was a rumor floating around that you couldn’t mix nitrogen and air in your tires. However, research indicates this just isn’t true. You can safely top off your nitrogen tires with air, and it won’t harm them.

It will dilute the purity of the nitrogen in your tires, but it’s better to keep your tires properly inflated than worry about the purity of the nitrogen.

What Are The Downsides To Filling Your Tires With Nitrogen?

While nitrogen in your tires has some definite perks, there are also a couple of downsides to consider. If your tires didn’t come pre-filled with nitrogen, the costs to fill them with nitrogen are substantially more expensive than air.

Due to the necessary purging of oxygen from the tires, you’re looking at approximately $25-$30 per tire. You’ll also need to consider about $2 to $5 per tire when you need a refill.

Another disadvantage to nitrogen tires is that nitrogen isn’t as readily available as air. If you have air in your tires, you can simply visit a local Service Center or use an air compressor at home. To maintain the nitrogen purity in your tires, you can purchase a small tank of nitrogen, regulator and high pressure hose from any local welding supply shop to service your tires.

How Much Does It Cost To Fill Your Tires With Nitrogen?

Some Manufacturers and Dealers are now filling the tires with nitrogen on Automobile, RV’s and Motor Homes before delivery. This typically adds about $70 to $175, a minimal price to pay. However, if your new RV, car or truck doesn’t come with nitrogen, you can expect to pay an additional $30 per tire to convert the air to nitrogen. To properly convert to nitrogen, you must purge the tire several times to eliminate any chances of air remaining in the tire. 

When Is Using Nitrogen Better Than Using Air

Using nitrogen is typically better when it involves tires with higher pressures or in heavy-duty applications such as RV,s Motor Homes and Semi Trucks. You’ll most often see nitrogen used in instances where consistency in tire pressure is of utmost importance. This is often the case in high-performance cars, racing, and airplanes. 

Is It Worth It To Fill Your Tires With Nitrogen?

Nitrogen in your tires is extremely beneficial and can increase the life of your tires. However, if your vehicle or tires didn’t come with nitrogen, you can convert your tire anytime.. Do you have nitrogen in your tires?

[Cubflyer]

It was an interesting conversation...

Something to think about....  'The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen. Air also has small amounts of lots of other gases, too, such as carbon dioxide, neon, and hydrogen'.** straight out of a science book...

So filling your tires with "air" gets you 78% there..... then, over time, as the smaller O2 molecules leak out, leaves you with a higher and higher % mix of Nitrogen.

If I start adding nitrogen as the O2 leaks out (natural purging) eventually I will have 99% nitrogen (78 nitrogen+21oxygen=99).  A 99% level I would think would give you 99% of the benefit of 100% Nitrogen.

When I built up high altitude (jet) aircraft tires, they all got mounted on the rim and serviced with nitrogen, no 'purging' was performed. 

Just something to think about....  

PS, I recommend using Nitrogen, and have a nitrogen bottle/regulator setup that I service struts and tires with, have had it for years and use it, I have not had to refill my bottle yet... when I do I believe it will cost less than $50.

Ken

 

[Harold]

I'll just point out the presentation of the material is a bit misleading.  Air is comprised of around 78% nitrogen (By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases.)  Nitrogen molecules in Air are the exact same size as Nitrogen molecules in a "pure" Nitrogen environment.  Nitrogen doesn't "Improve Fuel Economy" or "Improve safety" as the presentation of the data perhaps might like you to associate with Nitrogen, rather properly inflated tires is the key.  I have nothing against Nitrogen and using a high concentrate of Nitrogen to fill tires may work for you to help you properly maintain your tire pressure.  The very last sentence is rather funny "Do you have nitrogen in your tires?" - absolutely, I have 78% nitrogen 🙂

[cbr046]

And Nitrogen filled tires saving fuel economy?  Quite the opposite.  Air expands with temps and we see a 5-10 psi increase with air.  Higher pressures = lower rolling resistance = higher mpg.  Using the Les Schwab formula that's 1-2% gain with air.  Nitrogen doesn't expand like air does so it runs a lower pressure with less heating effect.  Lower mpg. 

That said, I'd still like to go the Nitrogen route.  Set and . . . . while not forget maybe not keep looking at my Tire Minder.  Plus I can use the bottle to recharge my motorcycle shock.  😉

- bob

[Rodger]

Actually the only variable that gives pure nitrogen a somewhat advantage is the fact you don't have moisture in it whereas air compressed in a normal air compressor does.  The vapor pressure difference between water vapor and air is what makes the difference with temperature variations.  But, for what we do with these coaches, it is negligible in it's affect.  It's an advantage to use pure Nitrogen to some degree with it being a gimmick for the most part.  What's really funny about the article is saying O2 (the second largest component of air) is smaller than N2, which it isn't. Interesting addition on the size of O2 vs N2 added below. Nice work!

Edited February 24, 2022 by Rodger

[Ivylog]

I’ll waste my money on something more useful than 100% nitrogen…beer.

[Nevada Rob]

YES

6 minutes ago, Ivylog said:

I’ll waste my money on something more useful than 100% nitrogen…beer.

YES!

[cbr046]

Quote

Nitrogen is the chemical element with the symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772.

And the Nitrogen lobbyist have been pushing it ever since!  🤣

- b

[Cubflyer]

Read the beginning and then the last three paragraphs..... unless you REALLY get into this kind of thing.....

 

Are Nitrogen Molecules Really Larger Than Oxygen Molecules?
The correct answer, with respect to “permeation”, is yes.
Graham’s Law Explained:
The Difference between Effusion and Permeation
There's often confusion associated with the molecular size, molecular weight and permeation properties of
oxygen and nitrogen molecules, and GNI is often called to task to explain why nitrogen actually migrates
(permeates) out through the rubber of a tire slower than does oxygen. We felt it best to leave it to the expertise
of Dr. Keith Murphy to elaborate on the scientific principles:
"Effusion" calculations are not appropriate for "permeation" of gas molecules through materials, such as the rubber of
tire walls. There is a fundamental difference in transport occurring through “effusion”, and transport occurring through
“permeation”.

Effusion would be appropriate, if the O2 and N2 molecules were passing through a relatively large passage way
through the tire wall, such as a leak. Graham's Law for "effusion" applies ONLY if the exit through which the molecules
pass is relatively large compared to the size of the molecules and does NOT obstruct or constrain one molecule from
passing through relative to the other molecule. O2 and N2 molecules are only slightly different in molecular size but
both are very small. Thus, to constrain one molecule's (e.g., molecule of type A) passage relative to the other's (e.g.,
molecule of type B) passage, that passage way size must be fairly close in dimension to the sizes of the molecules
themselves.

Graham's Law does not apply, if the passage way is very small, as occurs for dimensions of passage ways in-between
the polymer chains in a solid rubber, where the dimensions between the polymer chains do indeed constrain passage
of the larger size molecule, which is actually N2, compared to less constraint on the smaller size molecule, which is
actually O2.

It is often mistakenly assumed that "molecular size" correlates directly with "molecular weight". O2 does have a greater
molecular weight (32) than N2 (28), but O2 is actually smaller in size. Thus, O2 fits through the relatively tight passage
ways between polymer chains in the rubber more easily than does N2. The difference is size between O2 and N2 is
very small, only about 0.3 times 10 to the -10th meters (0.00000000003 meters).

Among the various descriptions of the sizes of molecules, that most applicable to transport phenomena is called the
"kinetic diameter" of molecules. The kinetic diameter is a reflection of the smallest effective dimension of a given
molecule. It is easy to visualize that a given molecule can have more than one dimension, which characterizes its size,
if the molecule is not spherical. O2 and N2 are diatomic molecules (two atoms joined by a chemical bond or bonds),
not spheres in shape but rather cylindrical in shape, akin to the shape of a tiny jelly bean. Thus, a "length" dimension
of the cylindrical shape is a larger dimension than the smaller "waistline" diameter of the cylindrical shape. In transport
phenomena, the molecule with the smallest effective waistline diameter is that which behaves as the smallest
molecule, i.e., has the smallest kinetic diameter.

Literature reports of kinetic diameters for O2 and N2 molecules, derived from several different types of experimental
measurements, give slightly different values, but all show that O2 has a slightly smaller diameter than N2. The
following examples expressed in Angstrom units demonstrate this (one Angstrom unit is 10 to the -10th power meters,
i.e., one-ten-billionth of a meter): from gas viscosity data, O2 2.96 and N2 3.16 (difference 0.20); from van der Waal's
interaction data, O2 2.90 and N2 3.14 (difference 0.24); from molecular refraction data, O2 2.34 and N2 2.40
(difference 0.06). Other experiments, less applicable to transport situations, such as from closest packing, when the
two molecules exist in a frozen solid state at very low temperatures, still show O2 to be a smaller size than N2 (O2
3.75 and N2 4.00, difference 0.25).

The reason that O2, despite a larger MW 32, has a smaller diameter than N2 MW 28, lies in the electronic structure of
the molecules. As indicated by quantum mechanical theory of molecules, the electrons of a molecule form a diffuse
"cloud" surrounding the nuclei of the atoms in the molecule. The electron cloud around the oxygen nuclei in the O2
molecule is smaller, more compact in size, due to attractive electrostatic interactions between the electrons in the
cloud and the greater positive charge of the nuclei of the O atoms in the O2 molecule. Each oxygen atom has 8
protons in its nucleus, while each nitrogen atom has only 7 protons in its nucleus. Thus, the overall size of the electron
cloud of the O2 molecule is smaller than for N2, in part because its electron cloud is drawn in closer to the O nuclei by
the greater positive charge on the O nuclei.

The dimension of the molecule's electron cloud defines the size and shape for a given type of molecule. When one
molecule bumps into another molecule, the outer-most extent of the electron clouds of each molecule repel each other
in that local vicinity of the contact between the molecules. Each colliding molecule's electron cloud experiences a
repulsion, due to the proximity to the like electrical charge of electrons around the other molecule in the collision. Since
like electrical charges repel each other (like-repels-like), the electrostatic interaction between the electron clouds of the
colliding molecules is repulsive. That repulsion effectively defines the size of the molecules.

O2 "permeates" approximately 3-4 times faster than does N2 through a typical rubber, as is used in tires, primarily
because O2 has a slightly smaller effective molecular size than does N2.

A relationship that governs "permeation" is based on Fick's Law of Diffusion and Henry's Law of Solubilities, which
takes into account the relative sizes of the molecules and their sizes compared to the very small passage way
dimensions in the solid material (such as a rubber) through which the molecules "permeate". Combining Fick's and
Henry's Laws yields the overall equation governing permeation of small molecules, such as gases, in material, such as
rubbers and other plastics.

Let's call the rate of permeation of gas (i), Ji, J-sub-i, which is simply the volumetric flux of gas permeation per unit of
time. Conveniently used units of Ji are cubic centimeters of gas per second, or cm^3/s.

Consider a sheet of the rubber, such as a section of the tire wall.

That flux of gas permeating through a material is directly proportional to the first three factors, below, and inversely to
the fourth factor, below:
1. the area, call it A (in units of square centimeters, cm^2) of the sample of the rubber - More flux of gas would occur, if
the area were larger, if everything else were the same;
next,
2. the driving force for transport across the wall, which is the difference in concentration of gas (i) across the tire wall -
for convenience with gases, a nearly exactly correct measure of this is the difference in partial pressures (pi) of that
gas (i) on the two sides of the tire wall (i.e., pi inside minus pi outside) - Obviously, a higher partial pressure (pressure
units are cmHg, centimeters of mercury, and remember that 76 cmHg = 1 atmosphere = 14.7 psi) inside versus
outside means there is more driving force to promote transport across the tire wall;
then next,
3. the intrinsic permeability P, call it Pij, or P-sub-i-sub-j, is the "permeability coefficient" for the particular material (j) for
that type of gas (i) - Note that various materials, i.e., different types of rubbers or plastics will permeate O2 faster or
slower depending on the details of solid state structures of the materials, and different types of gases will permeate
each material faster or slower depending on the relative sizes of the gas molecules, as well as on how soluble the gas
is in the solid material; then lastly,
4. the thickness L (in units of cm) of the material - you can see that if the tire wall were, say, twice as thick, one would
expect half the permeation rate (flux, cm^3/s), all other things being equal.

Combine these four terms, and you get the permeation equation:

Ji = [ Pij x A x (pi inside - pi outside) ] / L

flux = permeability coefficient of gas (i) in material (j) of the tire wall multiplied by area multiplied by the partial pressure
difference for gas (i) across the tire wall divided by the thickness of the tire wall.

Similarly, for the other gas (m), its flux would be:

Jm = [ Pmj x A x (pm inside - pm outside) ] / L

since it would have a different permeability coefficient in that same rubber (j) and a different driving force across the
tire wall.

So, the fluxes for different gases will be different, depending on the relative magnitudes of the permeability coefficients
of the two different types of gas molecules and the relative concentrations (partial pressures) of the two types of
molecules on each side of the tire wall (i.e., inside vs outside).

From the early part of this discussion, you will now recognize that Pi, where gas (i) is O2, is greater than Pm, where
gas (m) is N2, principally because O2 has a smaller kinetic diameter than N2 and thus O2 has a larger permeability
coefficient than does N2 - actually O2 has a permeability coefficient in a typical tire rubber material, which is about 3-4
times that of N2 in the same material. Permeation of O2 and N2 is primarily determined by size effects, because at
normal temperatures and pressures relevant to the discussions of tires, these gases behave almost perfectly as Ideal
Gases. As such, the differences in solubilities of O2 and N2 in most rubbers and plastics are too small to contribute to
differences in their permeability coefficients. The differences observed are essentially solely due to the slight
differences in the size of O2 relative to N2.

In case you wish to do your own calculations, the units for P (the permeability coefficients) most often used in the
technical literature are:

[ cm^3 x cm ] / [ s x cm^2 x cmHg ] and for convenience, a standard unit of permeability is called the Barrer, after
Richard Barrer, one of the early pioneers in studies of permeation in materials, such as rubbers and plastics. One
Barrer unit is:

1 times 10 to the minus 10th power [cm^3 x cm]/[s x cm^2 x cmHg]

In Barrers, for a typical rubber material, the permeability coefficient P, is dependant on temperature, but at 25C
(77F) for O2 is about 10 and for N2 is about 3.

I hope this helps clarify why O2 permeates faster through rubber than does N2 and a major aspect of why it is a good
idea to significantly reduce the amount of O2 used to fill tires by replacing most of the O2 in air with enriched N2. Since
N2 permeates through the tire rubber more slowly than would O2, using enriched nitrogen instead of air for tire filling
contributes to better maintenance of the proper inflation pressure for the tire. Better pressure maintenance contributes
to reduced tire wear, so that tires last longer and tire replacement costs are reduced.

A simple but approximately correct explanation of this lies in the mechanics of the flexing of tire walls. If proper inflation
pressure is maintained, the tire wall most effectively bears the weight of the vehicle. If pressure is allowed to fall too
low, extra flexing that occurs as the vehicle bounces somewhat along the road causes excessive mechanical fatigue of
the structure of the tire. Similar to flexing a wire coat hanger, this fatigue can weaken the tire faster than would be the
case were it kept inflated to a pressure more consistent with that intended in its design.

Dr. Keith Murphy
Air Products and Chemicals, Inc.
Prism Membranes
St. Louis, MO

[jegall]

Been using air in all tires for 70 years  including two motorhomes and 5th wheel just a sales gimmick.

 

[Jdw12345]

Fwiw, this is what Michelin says about nitrogen filled tires on OTR trucks and RV’s.

 

NITROGEN
The earth’s atmosphere is approximately 78% nitrogen, along with 21% oxygen, and 1% other gases. Nitrogen is a dry inert gas that does not retain moisture. While there are advantages for aircraft and large off-the-road earthmover tires to use 100% nitrogen systems, it is generally difficult to quantify the advantages for over-the-road highway operations. The predominant concern for proper tire inflation is moisture in the compressed air system. Moisture, when present in the tire, greatly accelerates
the oxidation effects to the tire and the wheel. Using well maintained inflation equipment (compressor, inflation lines, and in-line air dryer) will minimize the moisture content of the compressed air in the tire. Increasing the nitrogen percentage to 100% with a nitrogen inflation system will not adversely affect the inner liner of the
tires, nor negatively impact tire performance. Regular tire pressure maintenance remains critical, and tire inflation check intervals should not be extended due to nitrogen use.

Edited February 24, 2022 by Jdw12345

[Mike Harden]

I've been using nitrogen in my RV tires for the past 10 years & LOVE that my TPMS always stays green & OK. I did see an increase in fuel economy when I changed over to nitrogen due to my not being as careful about maintaining tire pressure balances when I was using compressed air. Since I changed over, I'll spot check my TPMS systems every once in a while and take an actual reading to make sure things are where they should be.... and so far...... they've always been on the money!!

Mike Harden

Memphis, TN

2004 Dynasty Diamond IV

2014 F150 FX4

[Ivylog]

I wonder if the cold psi from the charts is for 78% nitrogen air or 100 % nitrogen since it’s supposed to make so much difference. OH, never mind, I’ll go back to my beers.

[Rodger]

2 hours ago, Ivylog said:

I wonder if the cold psi from the charts is for 78% nitrogen air or 100 % nitrogen since it’s supposed to make so much difference. OH, never mind, I’ll go back to my beers.

Unless you put beer in the tires with your air or pure nitrogen, they'll be the same since they both pretty much follow the ideal gas laws.  Have another beer and Cheers!

Edited February 24, 2022 by Rodger

[jegall]

Let’s start rilling our tires with helium then we run lighter down the road . It’s all about correct pressure 100 psi is 100 psi no matter what you fill your tires with . 

[Ivylog]

24 minutes ago, jegall said:

100 psi is 100 psi no matter what you fill your tires with

Yes, but the amount the pressure increases is supposedly less with 100% nitrogen… one of its many advantages. The charts are based on the pressure increasing as the tire’s temperature increases which will be less  with 100% nitrogen. Do you need to add 5% more psi than what the charts call for???

 This is going to drive me to drinking in the morning or maybe not driving at all…  guess I’d better walk to the beer store.

Edited February 24, 2022 by Ivylog

[Chuck B 2004 Windsor]

IMO, if nitrogen is the greatest gas used in tires since Carter invented liver pills, everybody would be using it.  In my area, you cannot find a tire store that has nitrogen.  

[Chargerman]

So if tire pressure increases more with air vs nitrogen wouldn’t mileage be better when using air?
I just had to ask 🙄

Edited February 24, 2022 by Chargerman

[Paul J A]

A personal choice is simply that. Ran out of popcorn, so your on your own.

I meet a guy in Indio, Ca. in 11-2005 at a RV Park who was inflating his coach tires with a  powertank.com . He was a distributor for the product. I purchased a 15# Tank and all the accessories for the use of it. I had the tank filled with Nitrogen, MY choice. It was amazing. Filled coach tires from 105# to 110# in less than -1- minute. I installed it in the coach basement, with quick disconnects, and used a 50' hose to air up the coach and toad from either side of the coach. The tank of nitrogen would last 1 to 1-1/2 years between refills, costing between 12-14$  at Gas Supply businesses around the country as we were Full Timers.  I paid 495$ for it, and  Sold it in Spring of 2014 for 350$.  I would do it again

[jegall]

Just plain air from a compressor is 78% nitrogen so with 100% nitrogen the difference is so small I cannot believe that it’s going to make any significant difference in mileage.

[Ivylog]

3 hours ago, Chargerman said:

So if tire pressure increases more with air vs nitrogen wouldn’t mileage be better when using air?
I just had to ask

You may be a beer drinker too.

[granvillebarker]

21 hours ago, Chuck B 2004 Windsor said:

IMO, if nitrogen is the greatest gas used in tires since Carter invented liver pills, everybody would be using it.  In my area, you cannot find a tire store that has nitrogen.  

Just drive up to Starkville, it seems like every tire shop has a nitrogen machine.   ( probably just a dried air compressor ).  There must have been a good sales guy selling them.

[Bob Schmeckpeper]

Air is about 75% nitrogen. As soon as you have to use air to fill a tire because you can't get nitrogen, you now have to deflate that tire to refill it with nitrogen because you just lost any advantage that you had in the first place.  

 

https://lisbdnet.com/why-is-there-so-much-nitrogen-in-the-air/