Filling Tires with Nitrogen at home?

[xonetruthcrewx]

I agree that for everyday use, its not worth it. I use it for everyday use, but i get it for free. Where it is well worth it is on the track like i mentioned earlier. I sit there with my Nitrogen filled tires and never have to adjust my pressure. I watch everytone else constantly adjusting their pressures after each session. I remember a track day in my Audi. After one hard session my tires had increased 12psi. Thats huge. That kind of pressure change will cause major problems with traction on the track. If i had been running Nitrogen, it wouldnt have happened. This is my real world experience with Nitrogen vs. Air.

[bamachem]

Seriously, I agree that with 100+ degree tire temp changes, every little bit helps, but for every-day use and at ~$10 per tire - its a scam on the average consumer, which includes all applications of offroading.

Also, we're not going to piss on your parade here if you have an opinion and express it within the bounds of our rules - that's not how this place works.

It just sucks that we don't have a way of detecting sarcasm on these boards... I can't believe I fell for your bullshit!!!

[Robinhood4x4]

But this thread does have great tech that people in the future will find.

[RobG]

Any idea what temp a track tire gets too? 200F+?

The only thing that makes sense to me is they are converting the water to gas giving a large volume change and resulting pressure increase. Bottled N2 is very dry compared to standard compressed air (no dryer) so little to no water.

Street tires probably don't get nearly as hot so you don't see much difference there.

Is that possible?

[BruceTS]

Almost forgot we ran bleeder valves on our wheels to vent off excessive pressure when the tires heated up. I know bleeder valves are banned for use in the NASCAR cup series, mainly because after a tire cools, the pressure drop can cause more problems......OH wait did I say pressure drop? That's right, even with nitrogen filled tires, all NASCAR teams experience this..... What do I know? a simple search will yeild a wealth of information on pressure change in tires in all forms of racing.

I'll bet you won't notice a difference in a tire that is filled with nitrogen vs one filled from a SCUBA tank.

[Robinhood4x4]

The only thing that makes sense to me is they are converting the water to gas giving a large volume change and resulting pressure increase. Bottled N2 is very dry compared to standard compressed air (no dryer) so little to no water.

Is that possible?

Yes, that's what happening.

[bamachem]

here's another point of view.

we all know air is 80% nitrogen and 20% oxygen.

if nitrogen won't leak thru the rubber but oxygen will - as claimed by all the pro-nitrogen people - then wouldn't it make sense that you would eventually end up with all-nitrogen in your tire by filling with air anyway?

think about it.

lets say a tire holds 5 cuft of volume to make the math easier.

initial fill is 4cuft of nitrogen and 1cuft of oxygen.

tire leaks down, supposedly via osmosis thru the rubber. since the nitrogen proponents say that nitrogen doesn't leak down like air, then what's leaving the tire must be oxygen, by simple deduction using their logic, correct?

now, let's say you lost 1/2 cuft of oxygen and now you have the original nitrogen and have to add 1/2 cuft of air.

now you have 4.4 cuft of nitrogen and 0.6 cuft of air.

tire leaks down over time again. we loose half the oxygen.

now you have to add 0.3 cuft of air. at that point, you have 4.64 cuft of nitrogen and 0.36 cuft of oxygen.

leak down half of the oxygen again...

you get the point. you get to 99% nitrogen pretty quick...

[BruceTS]

The funniest thing about this myth is the claim of rubber deterioration. It's so silly how some people will believe almost anything. If you have ever looked inside a tire after it's been removed, they usually look brand new. Now how can this be? Duh the outside of the tire is exposed to more harmful effects than the inside will ever see. BTW if you think air is that bad on pressure change, check out the radical changes CO2 with temperature differences. OMG maybe we should have CO2 banned, since it's also a greenhouse gase and every time we use the stuff we are contributing to Global Warming

[bamachem]

i did some more reading and found some interesting info. it turns out that DRY air and nitrogen have very similar properties as i've been stating so far. however, when you add moisture to the air, the properties change dramatically. when you factor in thermal expansion of water vapor, increase in vapor pressure, as well as changing any condensed liquid to a vapor (~50X expansion in volume for a given mass at constant pressure), then you can see that the culprit is water vapor and not the use of nitrogen itself.

for everyday driving, it's still 99.9% overkill and really isn't economically sustaining considering that it costs as much as $10/tire. however, if you have access to dry compressed air or nitrogen for cheap/free, then you might as well use it.

here's what i found:

1. when comparing nitrogen gas and moisture-laden air, are pressures more constant with temperature changes? YES, nitrogen is better, and in extreme cases, considerably better. however, the same results could be attained by using dry compressed air instead of nitrogen. moisture is the culprit in the pressure differential, NOT the use of either nitrogen or air.

2. does a tire filled with air leak down faster than a tire filled with nitrogen? YES, but if you continue to refill a tire with air, then the oxygen will eventually diffuse, leaving highly-concentrated nitrogen behind. however this does NOT have the same effect as filling with dry nitrogen since the moisture is still present and, therefore, pressure fluxuations will still be the same as a tire filled with moisture-laden air.

3. do tires filled with nitrogen run cooler? No. Not directly via the use of nitrogen, anyway. Since they don't leak down as fast, they would statistically be operating at more-optimal pressure, resulting in less chance of overheating due to excessive friction - usually caused by underinflation.

4. do tires last longer when filled with nitrogen compared to air? Technically, Yes. Practically, NO. The rubber will not oxidize as fast when you fill with pure nitrogen, however, the chances of you owning a tire long enough for it to oxidize from the inside out before it either wears out, gets dry-rotted from UV/sun exposure is pretty slim. Today's tires are made from some pretty advanced compounds, and unless you plan on driving on a set for 10+ years, then you really shouldn't worry about (or buy into) the "lasting longer" jargan. However, if you look at it from a wear standpoint, with more consistent pressure on the inside, it's more likely to get a more even wear pattern, thereby leading to the possibility of eeeeking a few more miles out of a set.




http://getnitrogen.org/pdf/APTechLetter111804.pdf

1. Why does oxygen migrate out of tires quicker than nitrogen?
2. Why does nitrogen not expand and contract as much as air?

Answers:

1. Oxygen migrates out quicker than nitrogen, because:

a. Permeability coefficients measured for oxygen, P O2 , are higher than the values for nitrogen, P N2 , in all known rubbers (elastomers), including those typical of tires. The ratio of the permeability coefficients, P O2 divided by P N2 , is between 3 and 4 depending on the particular rubber. This means that oxygen permeates 3 to 4 times faster through rubber than does nitrogen, other conditions being equal;

b. oxygen is a smaller molecule than nitrogen (as determined by a wide variety of measurements of molecular size); this is true despite the fact that molecular weight of O2 (32) is greater than that of N2 (28), which might suggest that oxygen is larger than nitrogen;

c. relative permeabilities for oxygen and nitrogen are dominated by the difference in size of the molecules.

2. There is no significant difference in expansion and contraction characteristics of nitrogen, compared to air, when moisture is absent.

a. Expansion or contraction of either air or nitrogen occurs to very similar extent, in response to changes in temperature, in the commonly encountered range of temperatures and pressures relevant to discussion of tire inflation.

b. There is no practical difference as long as the gases are dry, with respect to the effect of temperature on pressure in an essentially fixed volume container, such as in a tire.

c. Water is usually present in the case for conventional compressed air. At lower temperatures, as a liquid, water occupies very little volume. However, as temperature increases, liquid water vaporizes to become a gas and its volume expands, causing total pressure to be higher in the tire, than would be the case with dry gas. Thus, the presence of water in a tire contributes to pressure variations as temperatures change.
Please find attached several pages of more detailed information. I provide a Summary, explaining in plain language several factors at play in tires, comparing using Nitrogen to using conventional compressed air. In Appendix, I provide more detailed technical information drawn from credible literature sources.

If I may be of further assistance, please contact me or our Sales/Marketing Specialists, Bill Phelps and Phil Powell in St. Louis.

M. Keith Murphy, PhD
Air Products Research Associate
(314) 995-3434
murphymk@apci.com





Summary - Nitrogen compared to conventional compressed air for tire inflation

Benefits:

1. Maintain proper tire pressure longer with Nitrogen than with compressed air

2. Reduced degradation of rubber’s mechanical properties caused by oxidation, in the absence of oxygen, using Nitrogen

Composition differences between membrane-generated Nitrogen and conventional compressed air:

Oxygen and moisture are almost completely removed from air by the membrane.

Explanations for the benefits of using membrane-generated Nitrogen compared to compressed air for tire inflation

1. Better inflation pressure maintenance using Nitrogen:

Nitrogen permeation through the rubber is much slower than oxygen permeation.
Measured permeability in all known rubbers is faster for O2 compared to N2,
by factors ranging from 2.4 to 4.7, depending on the rubber.
Permeability of gases is generally faster in some rubbers than in other rubbers, but
all rubbers permeate O2 faster than N2 by a ratio of about 3 to 4.
Oxygen permeates faster because it is a smaller molecule than is nitrogen.
Thus, any tire filled to proper pressure will hold that pressure longer,
if the higher permeability component (O2) is not in the tire in the first place.

2. Reduced oxidative degradation of rubber, because oxygen is absent, using Nitrogen:

according to J. D. Baldwin, et.al., (Ford Motor Co.), in “Passenger tires inflated with nitrogen age slower”, Rubber & Plastics News, pp. 14-19, Sept. 20, 2004
Oxygen chemically reacts with rubber, causing the rubber’s mechanical properties to degrade.
Nitrogen does not react with rubber. If oxygen is absent or present at much lower concentration, rubber mechanical properties are more stable over time.

Do tires run cooler?:

Tire run temperature is influenced by many factors, including:

Proper inflation
Rolling resistance
Road conditions
Speed
Outside environment temperature
Vehicle load
Temperature influences gas pressure.


Heating a gas in a fixed volume container increases gas pressure (P1/T1 = nR/V = P2/T2)
and cooling decreases gas pressure. For example,

a truck tire filled to 100 psig at 60F, increases in pressure to ~118 psig at 140F;
a car tire filled to 30 psig at 60F will increase in pressure to ~ 37 psig at 140F.

For temperatures and pressures near common experience, air, or O2 or N2, all behave very similarly in this respect. Thus, there is no significant difference in pressure changes, comparing air and N2, due to gas temperature effects alone (that is, as long as either gas is “dry”).

Water, however, can exist as liquid or as vapor (i.e., a gas) and water changes from liquid to vapor over the relevant range of temperatures. The “vapor pressure” of water is very sensitive to temperature, increasing from 0.26 psi at 60F to 2.89 psi at 140F.

If there is liquid water in the tire at 60F, as does occur with conventional compressed air, water’s vapor pressure contributes a small additional amount to pressure at 140F. If dry air or dry N2 is used to fill the tire, the effect of water on pressure is eliminated. Tire heating will be greater, if proper inflation pressure in not maintained.

Over time, a tire filled with air, will loose pressure faster, due to faster permeation of O2.
This will contribute to under-inflation of the tire, absent frequent pressure checks. Under-inflation may contribute to excessive mechanical flexing of the tire, which will contribute to additional road resistance and frictional heating. Thus, improper inflation is a principle contributor to excessive tire heating. Nitrogen helps better maintain proper tire inflation pressure, compared to compressed air.

Do tires wear longer?

Tire wear is influenced by many factors:

Proper inflation pressure (see above discussion)
Rubber’s mechanical properties are more stable, if oxygen is not present.