Uh, no. Not really.
Nitrogen’s covalent radius (1/2 the distance between identically covalent bonding nuclei) is roughly 75pm (picometers, 1 pm= 1x 10-12 m).
Nitrogen’s covalent radius is 75pm, so the length of a nitrogen molecule (N2) is 4 X 75pm or 300 pm.
A molecule of Oxygen (O2) is just a shade smaller, 4 X 73pm or 292pm.
So an oxygen molecule is little less than 3% smaller than a nitrogen molecule, not enough to matter.

But I’m usually in the garage and just cut it on, go check the oil, top off fluids, etc while I’m waiting. Not the quickest method to fill, but it’s also nice peace of mind when traveling. Most modern tire leaks are slow (not blowouts), so if I’ve got a slow leak far from home, I can just overfill slightly and get back on the road until I can get a patch.

“I left it running on one of my small truck tires for 20 minutes, and it wouldn’t pump any more than 33 pounds of air”

Someone else said it would do 5 psi in a short period.

I guess it’s best used for emergency/light use and hit a proper compressor for high PSI use.

But would increased pressure significantly reduce deformation of the tread? That doesn’t seem likely to me. However, I can easily understand that increased pressure reduces side wall deflection.

Higher pressure will cause the tire to stay rounder. The rounder it is, the less it’s deforming. Any change in shape due to load on the tire will involve deformation of both the sidewall and tread, but the tread contains most of the mass.

For me there is a free air pump at the Pilot Fuel Center off of I-40/Lovell RD that is very convenient from my house but when I move I might just follow ash78’s lead and buy a 12v air compressor. Since I have more than one vehicle it’d be nice to be able to deal with all the tires in one pass instead of doing them in batches.

I suppose a cold winter day after the frost is on the ground would give you drier air if you are going to compress it yourself, though humid air is better than a noticeably under inflated tire…

I’m interested, because I don’t want to clutter up the garage with a big compressor, yet am concerned that a 12 V DC one would be too slow to be practical.

See my comment above about a $9 Campbell-Hausfield air compressor from Walmart. It stays in my trunk and has a 10′ power lead to the 12v outlet in my trunk or console. About 9″ x 3″ x 6″ when packed.

Following Landcrusher’s comments; I think that the Federal EPA should mandate (and provide funding) for user-friendly (large, accurate PSI guages), free tire inflation at all gas stations, and TV commercials to promote their use. The “bang-for-buck” factor should be pretty high, as increased awareness/participation in the maintenance of proper tire inflation pressures (for both safety and fuel efficiency) would have fairly immediate benefits.

Thanks to Michael for the great article and to the commentators for the great information. I’ve seen billboards advertising the N2, but I had no idea why, and I figured that it was mostly a gimmick, and now I know, it mostly is. Funny thing is, I was just discussing this with a buddy last night – he said he’d heard that putting ‘air’ back in to an N2 filled tire could be dangerous. After I pointed out that there’s a lot of N2 in the air, he was relieved. This just goes to show how much confusion the marketing has managed to create.

I did just notice a local place that offers free N2, so maybe I’ll take my tires in there for a fill up – I do have one that seems to leak like a sieve, even though there’s no puncture.

My only question – do they first draw a vacuum in the tire to get all the O2 and other gases out? If not, I’m not really getting an N2 fill up, am I? If that’s the case, then lantius’s comment is right on – enough fill ups with the O2 leaking out equals 95% N2 content!

Both of these factors are either in very limited supply or unavailable on the inside of tires. The argument about interior tire degradation by O2 is completely specious on a human timescale.

I was going to say that Oxygen is larger because of the higher molecular weight, but after doing a quick Wikipedia search, I guess the nuclear forces make it smaller. Hm. You learn something every day.

ghillie, I believe it is mainly due to deformation of the tread mass and sidewalls. I’ve been told by a tire engineer that a tire’s fuel economy is primarily dependent on the mass of the tread. This makes sense to me since it is the mass that is continuously being deflected while driving, and less tire pressure equals more deflection.

Thanks for that rpn453

So it’s not to do with the increased friction between road and tire due to a larger contact patch.

I assume it is a combination of tread mass and tyre pressure. More tread mass, more tread to deflect (so some tire will be more efficient than others) but increasing the pressure reduces deflection for any given tire.

But would increased pressure significantly reduce deformation of the tread? That doesn’t seem likely to me. However, I can easily understand that increased pressure reduces side wall deflection.

I think most leaking is from valve stems, punctures, and rim seals.

Air is ~80% nitrogen anyway.

Most tires don’t fail from internal oxidation.

Also someone commented that nitrogen does not change pressure as much under heat. Not true – nitrogen, oxygen behave a nearly “ideal gases” and thus pressure change will be same under temperature.

I think big factor is quality of rim seal. Was wheel manufactured correctly? How about the tire? How careful are most shops mounting tires,even small particle will cause small leak.

Smart tire shops would use a Nitrogen fill at no extra cost and offer to check and top off anytime. This gives customers a reason to come back and also gives the shop a chance to do routine inspections to check things like alignment, shocks and brakes.

As others have already said, Costco fills new tire with Nitrogen at no extra cost. Other tire companies would be smart to do the same.