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One of our local tire shops is making the claim that inflating your tires with nitrogen will help your gas mileage. Have any of you guys heard of this or is this a lot of hot air so to speak?

From what I've read, nitrogen is a larger molecule and doesn't leak out as fast. Therefore you need to check tire pressure less. Also, the coeffecient of thermal expansion is lower (I think) for nitrogen. So, as the gas in the tire heats up, the nitrogen doesn't expand as much as oxygen which keeps your pressures more constant. This is a great thing if your racing, but for normal street driving its not worth paying for. Especially since we don't mind a few more pounds of pressure in our tires.

Thanks, that makes sense. I'd imagine the cost of inflating the tires with nitrogen probably outweighs any FE gains I would receive just doing normal driving.

I still don't understand how pure nitrogen is supposed to be more temperature stable than any other gas, especially air which is 78% nitrogen. The ideal gas law applies the same to both. The only real benefit I've heard of is that nitrogen is dry, so you won't wind up with water condensing and building up in your tires. Maybe it's worth it on that basis but I don't think it can be justified on the basis of performance.

Maybe we all should try helium or better yet hydrogen and hope there is no mini-hindenburg disaster.

Oh, the humanity!:D

If we all filled our tires (including the spare) up with Helium and the spare leaked inside the trunk/car we would all end up talking like the Telly Tubbies. :eek:

Consumer Reports' opinion:
http://blogs.consumerreports.org/cars/2007/10/tires-nitrogen-.html
http://blogs.consumerreports.org/cars/2007/10/nitrogen-tires-.html

Air is like 78% nitrogen. I really can't see any reason going to 95% nitrogen would do anything other than put money into someone else's pocket. But who knows...

-Gren

I had H2 @ 60psi put in my new set last year in September. I didn't check the psi for 12 months. They had lost about 7 lbs. I diluted it when I bumped them up to 70 psi with my Bostich compressor. I'm not going to do it again for $5 per tire. I had to drive about 120 miles round trip to even get it done.

Maybe we all should try helium or better yet hydrogen and hope there is no mini-hindenburg disaster.

Oh, the humanity!:D

You are onto something there. Nitrogen is my favorite gas for "inerting" potentially explosive storage tanks. It should keep your tires from combusting/exploding from within.:p

I had H2 @ 60psi put in my new set last year in September.

H2 :eek:

AWWWW MAN!!!! I hoped I could get home and edit that before anybody noticed. We just got a semi load of H2 in today so I had it on the brain!

N2 aka nitrogen. I like to live on the edge at times, but not like that!!!

N2 aka nitrogen. I like to live on the edge at times, but not like that!!!

Not to mention you wouldv'e lost a lot more than 7 PSI in 12 months if you'd used H2. It's a much smaller molecule, so it permeates porous barriers (e.g. tire rubber) much more readily.

Even going from air to CO2, which is a much larger molecule than H2, rapidly accelerates air loss. My wife's bicycle might lose ~20% air pressure between weekly rides. However, she's used CO2 cartridges to fill her tires a couple of times; when she did, the tires were flat the next day. CO2 is strictly a get-you-home measure, meant to be replaced with air ASAP.

The increased CO2 content in air over N2 is most likely at least partially responsible for air's increased permeability.

Personally, I just use air in a (bicycle) floor pump for my car tires. 10-15 pump strokes per car tire every couple of weeks, readjust with a gage and you're done. A bit easier than most bicycle tires, which require airing up at least weekly, if not daily.

From what I've read, nitrogen is a larger molecule and doesn't leak out as fast. Therefore you need to check tire pressure less. Also, the coeffecient of thermal expansion is lower (I think) for nitrogen. So, as the gas in the tire heats up, the nitrogen doesn't expand as much as oxygen which keeps your pressures more constant. This is a great thing if your racing, but for normal street driving its not worth paying for. Especially since we don't mind a few more pounds of pressure in our tires.

Spot on.