Nitrogen Results

regular air has o2 witch will burn/explode n2 don't.so the main reason for n2 is to prevent explosion and fire due to high heat generated by tires going from 0 to 180 mph in less than one second AND SPECIALLY to prevent tire fires due to hi heat generated during the breaking cycle trying to stop 150 tons from 180 mph to a full stop in a few seconds (like the airliners,military,nasa) but i don't believe it has much to do with significant mileage. improvement

 

Sheepdog -- getting testy.

I'll name just one thing I find of value that hasn't made money for someone. A hug. I got one from my little girl last night. She said: "Daddy, I didn't make anything special for your birthday, but I have this for you." She gave me the hug of a lifetime and wouldn't let go. No money maker in that one, but the value is measureless.

NASA and Nascar may use it, but they have uses and purposes that go beyond the ken of the driver of a passenger car. I don't think it is practical to have explosive bolts on my car door, nor do I need a full roll cage and a head restraint system to keep my helmet in the correct position. If I drove as fast as those guys and kept only inches from my neighbor's bumper, well, then, I would consider some of these things.

Again, the only reason I see for using nitrogen (and it better be 99% pure) is to keep from oxidizing my tires or my alloy wheels. I'll be replacing the tires due to exterior tread wear first, anyway, so I just don't see the value of the extra cost. More than that, I check and fill my tires in my own driveway, so I wouldn't want to be limited to going to a specific place just to get the tires back up to proper pressure.

(Oh no -- there I go again. Sorry.)

 

Priori, I did not intend to come off testy or angry. I apologize if you read it that way.

I personally have no investment in N2. I use it because it is free to me. It has not made a difference in mpg for me so far at 3K miles. I may never know if it has real safety benefits for me. I may never know if it has any real benefits at all.

I was defending it mostly from folks who seem to think it pure bunk and I believe that it is not bunk. It is just one more safety percentage in my bag of tricks.

It's funny that people that are so forward thinking can be so closed minded on something thats proven already. If it doesnt come from Japan or from a particular church of thought and show immediate mpg, it's disdained.

It's just one of the ways some in this forum have prejudices that confuse me.

 

An invaluable thing, a daughter's hug. Perhaps the reference should have been to financial value. I doubt you have assigned a dollar value to that hug.

 

This is not an issue of belief. Religion is about belief, nitrogen in tires is simple science. It is not a matter of being closed minded or prejudiced. Facts are facts, whether you choose to believe them or not. We have addressed this topic several times before, and I am not sure why I bother to repost, except that I hate to see people taken advantage of by unscrupulous tire dealers.

Filling tires with nitrogen is not pure bunk, but the benefits are very specific and not particularly valuable for passenger cars. Briefly, here are the issues:

1) Tire pressure - Nitrogen in tires behaves as an ideal gas. Its pressure rises and falls with temperature just as any other ideal gas. The diffusion rate of nitrogen is slightly higher than air, which means nitrogen will leak through tires at a slightly faster rate than air. The diffusion rate for both nitrogen and air is so low that this is not an issue. Water vapor is not an ideal gas. The partial pressure of water vapor will vary with temperature more than that of dry air or dry nitrogen. Removing the water vapor from air or nitrogen reduces tire pressure variation as related to temperature. Being able to consistently predict pressure variation is the main reason race cars use dry gas in their tires. Nitrogen canisters provide a convenient and relatively inexpensive source of dry gas in a race track environment, which is the principal reason that nitrogen is the dry gas of choice. Aircraft also use dry nitrogen for this reason.

2) Oxidation - Nitrogen does not promote oxidation, which means that rims and tires will not oxidize on the inside of a tire filled with nitrogen. Oxidation rates with air are so low that this is not a significant advantage. Tire oxidation is much larger on the outside where the tire is exposed to fresh air and sun. Wheel corrosion occurs along the bead seal where it is exposed to the outside elements. Nitrogen fill does not help with either of these.

3) Fire - Nitrogen does not support combustion. This is a real advantage for aircraft and race cars. Its value for passenger cars is minimal if not zero. Passenger car tires are never internally heated to the point where combustion could occur on the inside of the tire. Nitrogen on the inside of a tire does nothing to protect the tire from external combustion.

Given these facts, the only real advantage of using nitrogen for passenger car tires is in eliminating or reducing water vapor. The process of producing liquid nitrogen removes all water vapor, so nitrogen expanded from liquid is dry. This is where the whole tire shop nitrogen pitch gets interesting. Tires shops do not get their nitrogen in this fashion. Instead they use a device which increases the concentration of nitrogen in ordinary air. Typically this device has some sort of coined name like "nitronizer" or something of that nature. Ordinary air is almost 80% nitrogen, so the increase is marginal. The important factor is the removal of water vapor, which is the same whether using a "nitronizer" or ordinary air compressor. There is no advantage to using nitrogen fill from a "nitronizer" verses air from a quality air compressor, assuming both use the same desicator.

Tom

 

The saturation pressure of water vapor tells you the partial pressure of water vapor if the air is saturated with water vapor. It only increases 0.8psi between 50 and 100 degrees F. That's why the effect of temperature on humid fill air is insignificant at the temperatures passenger car tires experience.

Between 100 and 212 degrees F, it increases 13.7psi. That's why race cars require dry fill air. Their tires operate in temperature ranges where the partial pressure of water vapor would significantly change the pressure in the tire. Passenger car tires don't operate at those temperatures, so the effects of humidity in the fill air are much less.

Water Vapor and Saturation Pressure in Humid Air

 

A very good point. This is also why humid air is a problem for aircraft tires, since they are stored at very low temperatures. Water vapor in humid air would condense and freeze at those low temperatures, leaving an off-balance chunk of ice at the bottom of the tire - not really good when they spin up at landing.

Another point is that most tire shops mount tires with water based lubricants. First you slop a bunch of water inside the tire, then you charge extra for "dry" nitrogen.

Tom

 

It is time for me to apologize, Sheepdog. I was just trying to have a little fun with you. Perhaps I didn't come across as "light" as intended.

We all have either blinders or lapses in judgment at times. Truth only comes one way, but it sure can be difficult to describe it, much less understand it. I understand you find that whatever the marginal increase in safety is, it has value to you. I believe there is a marginal increase in safety, but I just find it too small to be of consequence when applied to my use -- particularly if I have to pay for it. If I could get dry nitrogen for free, I would take it. If I have to choose between nitrogen in my tires or two gallons of gasoline or lunch, I won't be choosing the nitrogen.

Moi aussi. My own prejudices are confusing enough to me.

I have a very strong bent toward scientific analysis, but this often gets in the way of dealing with values that have no measurable quantity.

I hope not to have contributed too much (just my fair share!) to your confusion over the reasons behind people's varied responses to ideas and questions on this forum.