spf4000

Does anyone get their tires inflated with nitrogen? I hear this offers a variety of benefits over simply inflating your tire with compressed air.

1. Air doesn't leak out as quickly
2. Doesn't oxidize the inside of the tire (or wheel)
3. Doesn't change temperature as quickly

Now, before you make comments like "normal air contains 78% nitrogen already, so what's the point of filling it with 100% nitrogen", realize that normal air contains oxygen and water, which can cause problems inside the tire (oxidation and pressure fluctuation).

I've been looking around for a place in the bay area that offers this service, but I haven't had any luck. Does anyone know of a place?

jackwhale

You mean that oxidation on the inside of the tire contributes to shortening tire life? I wouldn't expect racing teams to use nitrogen because they wear the outside of the tire so rapidly. I wonder who would benefit--it will be interesting to follow the responses to your question.

Would helium or hydrogen effectively reduce unsprung weight? Of course they would leak out so fast, the tires would always be half-flat

ZpikeZ

Not sure if it would reduce unsprung weight, but i know that helium and hydrogen are flammable.

Flammable tires + blowouts on highway = major explosion.

Audito350Z

iTrader: (1)

you can use 100% nitrogen if you never want the pressures in your tires to change.... some race teams might use it for this reason. Let's them better control the suspension settings.

For daily use, go right ahead... but you have to pay to fill with nitorogen. If I need air, I turn on my air compressor and 5 minutes later the tires are all better.

PeteH

spf4000

One benefit I could see for racing is that since the nitrogen does not expand as much as regular air, it is less prone to blow outs and maintains a more consistent air pressure in the tire.

Other benefits I've read about for non-racing applications are:

-Better ride
-Less tire noise
-Better gas milage

I'm not really sure if these are really true. It might just be people trying to justify spending money to fill up their tires.

spf4000

Helium is one of the noble gasses, so it's very unreactive. Therefore, it would never explode. Now, hydrogen, on the other hand, goes BOOM.

vova151

What about Nitrous Oxide? Make the tires spin faster?

If you lose a race you could suck on the valve stems and laugh your worries away!

jackwhale

I'm surprised that the physical properties of nitrogen are really that much different than air.

OH great NOBLE gas!! I had forgotten about noble gases...that makes helium sound even better.

vova: This may be a patentable idea for dealing with road rage.

bunsell

The military uses nitrogen for their aircraft tires, not sure if civilian planes do. You might check with your local airport maintenance people.

2003z

iTrader: (7)

airlines use nitrogen too. They tend not to explode as bad if there is a brake fire.

CluelessZ

Helium=Noble gas, or a better term would be inert. Has no combustable properties.

ares

iTrader: (2)

Id love it if the pressure wouldnt change, I always fill up warm tires in the middle of the day, and then in the morning, Im suddenly setting off the TPM alarm. just so 10 minutes later Im at 33PSI again.

spf4000

Ares, my sentiments exactly. I want it so that the tire pressure does not fluctuate so much. I've noticed that my tire pressure goes from 34-39 during my morning commute (40 during spirited driving).

jackwhale

I'm surprised that the physical properties of pure nitrogen are that much different from an 80% mixture (pure air). The rubber in the tire heats up with the flexing and friction of driving and that heats the gas inside the tire. It would be interesting to know what is behind the military using it in their aircraft. Pure nitrogen wouldn't fuel a fire but....

I wish I had saved my old p-chem textbooks.

Murry

Nitrogen as a gas is N2 and since a nitrogen atom has a molecular weight of 7 the molecular weight of nitrogen gas is 14. By way of comparison air has a molecular weight of approximately 29. A tire filled with nitrogen gas will be lighter and have a lower moment of inertia than a tire filled with air. I can not think of any other practical advantages.

The thought that a tire filled with Nitrogen gas won't change temperature or pressure is totally incorrect. The ideal gas law (PV=mRT) shows the relation between temperature and pressure. Heat transfer will occur raising the temperature inside the tire and the pressure no matter what gas is used to inflate the tire.

I hope this helps and I anyone else has more information I would like to hear it.

-Murry

Murry

A nitrogen atom has a molecular weight of 7, but because nitrogen gas exists as N2 it has a molecular weight of 14. Air has a molecular weight of around 29. Therefore, a tire inflated with nitrogen will be lighter and have a lower moment of inertia than a tire inflated with air. This is the only advantage I can see.

It doesn't matter what gas you use when the tire heats up from friction the pressure inside the tire will rise accordingly. If we assume that the ideal gas law is practical for this analysis the temperature and pressure are related by pV=mRT. As long as no gas escapes (If it does you have other problems) the equation should hold reasonbly true.

If anyone has something else to add I would like to hear it.

jackwhale

Nitrogen has an atomic number of 7 and an atomic weight of 14.
Oxygen has an atomic number of 8 and an atomic weight of 14.

AndyB

Ok, here are my $0.02. this is not a flame, but since I am correcting errors it might seem like one. Just remember my intent is not to flame.

First of all, as you said, air is mostly Nitrogen. (78% or so) Let me address the other thoughts on this thread.

1. Nitrogen doesn't leak out as quickly. Sorry. Oxygen is a larger atom/molecule than Nitrogen and is typically found in O2 form. Nitrogen is much more likely to leak or permeate through the rubber.

2. Nitrogen doesn't oxidize the inside of the tire (or wheel). I have never heard of tire life being affected by oxygen from the inside. In fact, compared to the abuse the outside takes (friction, oxygen, salt, polution, etc) I would wager that oxygen inside is NEVER a concern in normal use for a car tire.

3. Nitrogen doesn't change temperature as quickly. It doesn't? Maybe you mean it expands less with heat? In that case I think the difference caused by the additional oxygen would be far less than you could measure with your pressure gauge.

The water would only change the pressure if you heated the inside of the tire above the boiling point of water. Below that, it would remain liquid/vapor (and thus non-compressable). Also, the boiling point would be higher than 100 degrees C due to the elevated pressure.

As for Helium or Hydrogen, good luck! A tire inflated with helium or hydrogen would lose pressure VERY quickly compared to air. Both Helium and Hydrogen are TINY atoms and would leak MUCH faster than Nitrogen or oxygen. If you blow up two latex balloons, one with helium and one with air, the helium ballon will be flat in like a day. That's one reason weather ballons are mylar now.

Even if it didn't leak (assuming perfect seals and non-permeable tires) the weight of the air in the tires is miniscule. The pressure may be measured in pounds, but the weight of the air would be better measured in grams. You could shave more weight by doing a couple of quick burnouts and shedding a layer of rubber. You could even shed more unsprung weight by just taking a file to some random spots on the suspension arms.

I can understand your thought process but I seriously doubt anything proposed on this thread so far would make any measurable difference to pressure fluctuations due to heat or to unsprung weight.

Murry

I admittedly made a rookie error by confusing atomic number and molecular weight. It's nice to know some of the people on this board are intelligent and informed.

Are you telling me that the temperature inside a tire is above the boiling point of water @ 3 ATM absolute? And that nitrogen is used to eliminate the partial pressure exerted by steam?

If that's the case why not use a desicant dryer on a compressor?

BTW
density of Air @ 300K 1.16 kg/m^3
density of N2 @ 300K 1.12 kg/m^3

Therfore N2 is approximately 3.5% less dense than air. Anything less than 5% isn't worth considering.

I'm confused what is the real reason people have used N2?

jackwhale

Murry: I agree that physical properties (not chemical properties) of hydrogen, oxygen, air do not significantly differ from one another. The pressure change for all three is directly proportional to the temperature change.

Are we certain that the military uses nitrogen in its airplanes? The logic seems to be that if the tire breaks, the lack of oxygen means that it would not fuel a fire.

I wish I had not made the joke with Vova151 about helium and hydrogen and nitrous oxide because it certainly has become a distraction.