They use nitrogen in planes for several reason: Less air loss during temperature extremes, keeps moisture out for rust, you don't have to worry about it freezing when at altitude, and to keep the heat down when the tires go from 0 MPH up over 130 MPH or more when landing and taking off. Not to mention the incredible heat generated by braking. It's really amazing when you think about the abuse they receive and how much weight they support.
I can see the use of something with even a slight increase in safety, especially when it comes to tires in the aircraft industry. I'm not sure if it's just me, but I've noticed that when possible, commercial pilots resist reverse engine thrust and only use the brakes on landing, consequently using the whole runway. Is fuel cheaper than brake linings? They are doing this even in non-noise reduction areas and on large airliners (MD-80s on American specifically). This has to heat up the whole assembly tremendously.
Back to cars, I'm tending to agree with AlexK on the physical properties of Nitrogen and atmospheric gas makeup, and that it's probably all lights-and-mirrors in the auto industry.
This is my first post here... I had to comment on this.
I cannot see how nitrogen in tires would keep them significantly cooler than air. The specific heat of nitrogen is about 30% higher than air, but there simply isn't enough mass there to really make a difference. The mass of the tire and rim dominates the situation. Could it be viscous heating of the gas due to tire rotation? I think the gas would simply rotate with the tire and not have much viscous dissipation.
Also, how can nitrogen leak so much more slowly than air? Air is 78% nitrogen, so is the oyxgen leaking out? If so, eventually we would be left with just nitrogen in our tires anyway, as the oxygen is leaking out and leaving the nitrogen behind.
Nitrogen rises in pressure when heated the same as air does (neglecting very tiny differences to to gas compressibility, on the order of 0.05%). Most all gasses behave like ideal gasses at low pressure and temperature (much less than critical pressure/temperature).
I could see a benefit with corrosion but honestly, when was the last time a rim rusted away from the inside out?
I say it's a scam.
Before you say I don't know what I'm talking about, I'm an engineer in the R&D department of a company which makes instruments to measure gas flow. I know a little bit about gasses. I also have a masters degree in mechanical engineering (heat transfer and fluid mechanics). I do like to learn new things though, if I'm wrong please explain.
Right on, Alex! The Ideal gas law sez: All gases behave the same way"...right? I believe some NASCAR types started this nonsense (they're good at straw-grabbing!). -Ted Hart
Nitrogen helps prevent combustion and is very dry so you get rid of the freezing moisture problem in aircraft. In a car I can't see much difference but I did have the inside of a rim on my BMW motorcycle get all chewed up from liquid tire balancer. Nitrogen is a little less dense than oxygen atomic weight Nitrogen 14.00674 vs Oxygen 15.9994 in the periodic table.