Nitrogen in tires?

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Permalink Reply by Dan Hall on February 28, 2009 at 7:38pm

I looked into doing the nitrogen thing only to find out how expensive it was and that simply checking air filled tires on a very reqular basis does the trick in keeping the tires at proper inflation. I decided that it wasn't worth the expense and hastle to use it.
Dan Hall

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Permalink Reply by SATO on March 1, 2009 at 8:53am

Rachel, I by no means have my smarty like your Miata BUT I do have nitrogen in all my 3 cars. I get it free so cost is not the issue and the inconvenience of slow deflation is gone. Some swear by it and others just scoff using it with a regular rim.... let me explain... in order to truly have 100% nitrogen in your tires you will need to have two valves per rim. one would be used to introduce nitrogen and the other to extract the air. By using only one you will have some air left in the mix ALWAYS.

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Permalink Reply by Scott Mankewitz on March 1, 2009 at 4:29pm

Don't think I am totally stupid, but what does the nitrogen do?

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Permalink Reply by smarttask on March 1, 2009 at 5:26pm

Oh, there are plenty of benefits: (1) Cool fluorescent green valve stem caps (assuming your nitrogen vendor has any marketing savvy), which will look sharp with your spinning wheel covers. (2) Bragging rights. OK, you were behind the curve with cell phones, iPods, thong underwear, etc. Nitrogen in tires is relatively new to the mass market. Now's your chance. (3) Reduced fire danger next time you land your space shuttle or commercial aircraft, and tell me you won't sleep better knowing that.

Most tires are filled with compressed air, which when dry consists of about 78 percent nitrogen, 21 percent oxygen, and 1 percent other gases by volume. Water vapor (humidity) can make up as much as 5 percent of the volume of air under worst-case conditions. Filling your tires with nitrogen mainly does two things: it eliminates moisture, and it replaces skinny oxygen molecules with fat nitrogen molecules, reducing the rate at which compressed gas diffuses through porous tire walls. That means, theoretically at least, that a tire filled with nitrogen retains optimal pressure longer, leading to more uniform tire wear and better gas mileage. The commonly quoted figure is that tires inflated to 32 psi get 3 percent better mileage than at 24 psi.

Does nitrogen make any practical difference? You couldn't prove it by me. I found no scientific tests showing that nitrogen-filled tires stayed inflated longer than average under normal conditions. A car-buff buddy was sure it worked but conceded he had only anecdotal evidence that it did.

As for moisture, changes in humidity affect tire performance two ways. First, the density of humid air fluctuates more with temperature than that of dry air, so removing humidity can keep your tire pressure more consistent, especially when the temperature climbs over 100 degrees Fahrenheit. That may be a legitimate concern in Formula One racing, but it's not much of an issue if you're just tooling around town.

Humidity can also be a factor in wheel maintenance - since pure nitrogen doesn't have moisture in it, supposedly your wheels won't rust as quickly, which could lead to improved wheel performance and air sealing. The question is, how big a problem is wheel rust these days? According to a few tire and wheel shops we contacted, not very. Seriously rusted wheels are uncommon in typical steel-wheeled cars, and many high-performance cars have alloy wheels that don't rust at all. One exception is work vehicles such as dump trucks, which are exposed to a much harsher environment.

Another claim I've seen is that since nitrogen is slightly lighter than air, you'll save weight and get better performance. However, we're talking about a weight difference of less than 4 percent of the gas in the tire - in other words, a difference of less than an ounce for most vehicles. A possibly more realistic benefit is that nitrogen is largely inert chemically at low (i.e., normal) temperatures, so it won't attack the rubber in your tires like oxygen does. Oxygen attack is something both the National Highway Traffic Safety Administration and Ford Research have studied, and can be a problem for tires used for a long time or in rough conditions.

More important, nitrogen doesn't support combustion, which is one reason aircraft and the space shuttle use nitrogen in their tires. The wisdom of this precaution was brought home by the crash of Mexicana Airlines flight 940 on March 31, 1986. Shortly after the Boeing 727 took off from Mexico City en route to Puerto Vallarta, an overheated landing-gear brake caused a tire improperly filled with air instead of nitrogen to overheat as well and explode, rupturing fuel and hydraulic lines. The ensuing fire and crash killed 167 passengers and crew. However, unless your driving habits are of the X-treme variety, the chances of your tires catching fire anytime soon are slim.

Overall, filling up with nitrogen won't hurt and may provide some minimal benefit. Is it worth it? If you go to some place like Costco that does it for free with new tires, sure, why not? Elsewhere, though, I've seen prices quoted as high as $10 per tire, which is way more than I'd pay. Rather than shell out for nitrogen, you'd be better off just checking and adjusting your tire pressure regularly, something the NHTSA says less than 60 percent of U.S. motorists actually do.

Roger

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Permalink Reply by SATO on March 2, 2009 at 11:48am

Oh, there are plenty of benefits: (1) Cool fluorescent green valve stem caps (assuming your nitrogen vendor has any marketing savvy), which will look sharp with your spinning wheel covers. (2) Bragging rights. OK, you were behind the curve with cell phones, iPods, thong underwear, etc. Nitrogen in tires is relatively new to the mass market. Now's your chance. (3) Reduced fire danger next time you land your space shuttle or commercial aircraft, and tell me you won't sleep better knowing that.

You mean if I fill my tires with nitrogen I dont have to wear a thong to be cool???

Oh the Nitro fill at MB is $80 buckaroonies!!!! NO I did not get it done there, I just asked and then had to struggle not to make a wild face and laugh in their face...

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Permalink Reply by smarttask on March 2, 2009 at 12:38pm

I think you should keep wearing the thong, you don't want to spoil your image...............
Have'nt seen the "cool fluorescent green valve stem caps" over here, they give you red ones.
Roger.

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Permalink Reply by SATO on March 2, 2009 at 4:19pm

my image could only improve with a massive make over like those on TV..I doubt a thong would suffice LOL....

the valves we get here are not fluorescent but they are plastic and they are green. for some reason I think they cannot be metal, as it was very clear that they were PLASTIC.. well you would think that they would not advertise them being a cheaper plastic than perhaps a nice alluminium....

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Permalink Reply by Brabus007 on October 14, 2009 at 10:39am

~Seeing as were talking about AIR~We Best AIR This Subject OUT~

~Don't Be The Fool~Don't let them laugh at YOU all the way to the BanK~
NOTE: If you do top off your tires regularly, and it is the oxygen leaking out, with the nitrogen not leaking out as fast, what is left in your tire after many months? I would think it would be mostly the nitrogen.

Nitrogen is probably another example of an industry trying to make more money by selling you something you just do not need. Using dry nitrogen in your tires would mean that the 21% of air that is oxygen and a tiny bit that is water vapor will not be inside your tire, but remember that ordinary air is 78% nitrogen to start with. There are a number of claims of improvements due to using nitrogen...

One claim is that nitrogen reduces oxidation of the rims and the rubber as there is no oxygen or water inside the tire. Nice claim, makes sense on the surface. But I have never seen any signs of oxidation in my rims even on my currently 12 year old vehicle, never had a tire fail due to deterioration of the rubber or even heard of such a thing. A tire is likely to wear out long before rubber deterioration becomes an issue, if it was the tire companies would be getting sued left and right due to failing tires.

Another claim is that tire pressure changes less due to temperature. As long as all of the components remain a gas there is no difference in the temperature/pressure performance of pure nitrogen versus air, you get about 1psi for every 10°F change in temperature. The claim is that when the water condenses it will reduce the tire pressure. In the higher pressure inside the tire the temperature that water will condense is much lower than the same air outside the tire. It is unlikely that this is a major problem.

The one claim that seems to be something to consider it that nitrogen permeates (leaks) through the rubber more slowly than oxygen meaning that the tire will loose pressure at a lower rate than a tire filled with only air (You Still Lose Nitrogen At A Little Slower Rate). Claims are 1-4psi per month less loss meaning you will get better fuel efficiency and lower tire wear due to low pressure tires. This is easily dealt with by simply checking tire pressure regularly.

Another interesting thought... If you do top off your tires regularly, and it is the oxygen leaking out, with the nitrogen not leaking out as fast, what is left in your tire after many months? I would think it would be mostly the nitrogen.

There are some places where nitrogen is used regularly...

Racing teams generally use nitrogen to fill tires. But these teams also tune the cars to a very fine degree to shave fractions of a second off a race. Drivers claim to see handling differences with very small tire pressure changes (not being a race car driver myself this seems odd). So getting the water vapor out of the tire might make a difference in handling. These are changes that will just not be noticed in a non-performance vehicle like your SUV or minivan.

Aircraft tires are routinely filled with nitrogen, but then consider the conditions aircraft tires are subjected to. They sit on hot asphalt, with temperatures of well over 120F and a few minutes later they are at 30,000ft where the temperature might be -40F. When this cycle is reversed they are expected to survive many tons of aicraft hitting the ground. Frozen water in the tire could be a bad thing, it could freeze on one side of the tire while in flight then create an off balance tire when the aircraft lands. Just a little more extreme environment than your average passenger automobile.

Handling nitrogen is easier on an airport flightline where personnel can be trained in it’s safe use, it is usually stored in liquid form which can be dangerous to the novice. Nitrogen is already available on the flightline as it is needed anyway for pressurizing aircraft struts and hydraulic systems.

So for automotive uses you should save your money, use plain old air, and remember to check your tire pressure more regularly.

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Permalink Reply by mr bad example on October 14, 2009 at 1:36pm

yes, i agree, use plain old atmosphere. the thing that loses "air" is the porosity of aluminum wheels. people with old fashioned stamped steel wheels have lower pressure loses over time. now more and more cars have optional or standard aluminum alloy wheels. i think the increasing usage of alloy wheels and the new TPMS technology has brought tire pressure to everyone's attention.

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Permalink Reply by SmartGurl on November 10, 2009 at 10:44pm

I absolutely loved reading all of these responses. The smart community simply rocks, like no other. The wealth of information given was insane, in a good way. The best part was when I was reading this (after hours at the shop) Boris hears me giggling from across the room and asks what I'm reading; it's this thread.

I'm going to stick with good ol' expensive air and keep the mixed gases for when I go diving under the sea. Thanks so much everyone and please feel free to keep adding, because this thread is fun!

To you, yours and your smart!
rach

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