Comments on: Fuel Economy Tip – Fill Your Tires With Nitrogen?

By: Nancy

Nancy — Mon, 25 Oct 2010 00:24:46 +0000

I want to know if I use regular air in my tires will it mess the sensors up in my car and will it cause it to fail inspection if these are not working?

By: Kathie Jackson

Kathie Jackson — Wed, 26 Aug 2009 22:44:23 +0000

I came to read this as I have had some questions about my Nissan Xterra (08) which I just purchased. I was having trouble with a tire sensor coming on after taking it to a dealer, he said the tire sensor was burned out by water in the tire. He said when they pulled the tire they dumped out about a 1/4 ro 1/2 cup of water from the tire and this water was what burned out the sensor. He said a new sensor would cost about $300. I said , thanks but no thanks, I can drive with a sensor light on and further more, I never had one before and knew how to check my own tire pressure without a sensor. I am so irritated by this. he claimed that he had no idea how water got in the tire. now I find out that the tire was Nitro filled. It makes sense that something about this story involves that gas and the water and the sensor. I am just really ticked off and don’t know who should really fix this sensor but because I had never touched the tires it would not be me. Furthermore, what happens to a nitrofill tire if someone adds regular gas station air to it? Does that cause a problem? Thanks for the venting…

By: Dr. Steed

Dr. Steed — Fri, 27 Mar 2009 14:47:23 +0000

The presence of water only makes a difference if there is some of it present in liquid form initially. Here are some calculatons:

If I take a tire of 23 litre volume and fill it with 100% pure nitrogen (not what you will get in practice) to a pressure of 32 psig at 65F, and heat it to 130 F, the resulting pressure will be 37.9 psig. If I take the same tire, but now fill it with bone-dry air and add the same heat, it will end up at 130.1 F and 37.9 psig. If I again take the same tire and use saturated air at 65F to inflate to 32 psig, I will end up with 1.42 mol% liquid water. I will also have to inject a little bit more air than in the previous case to account for the water condensation. Applying the same energy will result in a final condition of 97.7 F and 35.5 psig.

Now if both tires were exposed to identical driving conditions over an extended period of time to equilibrate the heat generated through flexing with the heat loss, both tires would end up at the same internal temperature. Let’s say this temperature is 130 F. The tire filled with moist air would then end up at 38.6 psig.

These calculations were based on the Peng-Robinson Equation of State.

I do not consider these differences significant. I own a 66 Mustang which I have had for 30 years. I have only changed the tires twice. It is only driven in the summer and I have had to replace them because of uneven tire wear (wheel alignment). I have never observed any internal rotting. I have just measured my tire pressures on this car after being in storage for 5 months. All tires but one are still at 32 psig. One tire was flat because of a nail. I don’t think nitrogen would have helped me here.

I also own a 2004 Mustang SVT Cobra. On this vehicle, I have only had problems maintaining pressure in 1 tire, again due to a nail. I have had to replace them after 3 years because of external wear. Frequently pulling 0.99g on cornering has its toll.

I have a compressor in my garage at home which I check monthly for water. I have never drained water, even during periods of time of high daily temperature swings.

So to answer the question, would I put nitrogen in my tires? If I had to pay for it, no way. If it was free, not if I had to go out of my way for it.

By: Mike

Mike — Fri, 06 Mar 2009 03:09:40 +0000

Yes professor nitrogen will expand and contract,but not to the same extent as compressed air which contains water,Therefor when done the right way it does make a difference. The ride and handeling is consistant, the fact that there is no moisture inside the tire means that the rubber is not dry rotting. Finally I have had nitrogen in my tires for about 3 years, I have not had to add any to this point, you have nothing to loose by trying it.

By: Dr. Steed

Dr. Steed — Sat, 07 Feb 2009 19:45:39 +0000

William:

Nitrogen will expand or contract as temperature changes. It is a gas! It will expand to the same degree as air or pure oxygen. I happen to be a thermodynamics prof, but I advice you to check your high school science texts,

By: Bob Matiska

Bob Matiska — Fri, 27 Jul 2007 00:47:39 +0000

Nitrogen doesn’t expand when heated nor contract when cooled? Sure it does, just like all other gasses. And nitrogen, with an atomic number of 7 and an atomic weight of 14, is larger than oxygen, with an atomic number of 8 and atomic weight of 16? Since when?

OK, somebody here do us all a favor and buy 4 new tires, then have two inflated with air and two with nirogen. Keep track of the pressures with a good gauge for a few months and let us all know how the pressures hold up.

By: William Wilgus

William Wilgus — Mon, 09 Jul 2007 23:53:39 +0000

The advantage of nitrogen as a tire inflation gas is that it does not expand or contract with temperature changes. Theoretically, then your tires would always be at the recommended pressure. The advantages to this are that the tire does not expand when heated—increasing the life of the tire—and the tires’ road-holding properties remain more constant. This latter advantage is only important in racing or high-performance driving, or course.

Regardless, simply adding nitrogen does little good if you don’t evacuate the air from the tire first—or during the process.

By: Pal

Pal — Fri, 08 Jun 2007 21:15:19 +0000

“Pure air” is 78% nitrogen already, with just 20% being oxygen. If a person thinks that the pure nitrogen injection is the magic bullet for ignoring their tire pressure they should reconsider. You should always check your tires when getting gas, and inflate tires that will naturally lose pressure over time.

Show me a test where a tire is inflated with “normal air”; after running the car for a few weeks on a dyno or around town to allow the tires to lose some pressure, the tire is vacuumed out; the gases pulled out are tested and shown to have noticeably more nitrogen than oxygen, compared to normal air. I seriously doubt such a test has been done by any credible source.

This is really just another way of admitting to a sales person that you can be swindled out of money with fancy words.