My uncle stopped by today to ask me to install some new wiper blades on his '02 Accord, and I noticed some nasty LIME GREEN valve stem caps on his wheels. I asked him what the deal was, and he told me also got new tires at Costco, where they are now inflating tires w/nitrogen instead of regular air. He was informed that many tire places are doing this.

WHEN did this happen, and WHY??

Btw, all I know is those LIME GREEN caps are FUGLY!?

 

Something about less variation in tire pressure due to heat. By the time I post this, someone will have probably answered it better.

 

It is more stable with regards to heat mostly because of not having other gasses and vapors dissolved in it, also oxygen reacts with rubber over time and eventually degrades the inside of the tire faster than what happens with something more inert like Nitrogen is used to fill it...

But the main reason I've heard of was because Nitrogen doesn't have all the water vapor in it that compressed air does.


Wait- heres something else I hadn't heard;

"Air diffuses through tires 30-40% faster than nitrogen resulting in under-inflated tires. The US Department of Energy estimates that the USA could save two million gallons of gasoline every day if our tires were properly inflated. Furthermore, "Tires sometimes fail on the road due to blow-outs which may be caused by weakening of the tire's internal steel belts. Research indicates that elimination of air containing oxygen as a pressurizing medium would substantially reduce this weakening and reduce the number of tire failures."



An estimated 30-50% of all vehicles on the road are operating with under-inflated tires resulting in decreased fuel economy. As gasoline prices increase this issue will become all the more important for consumers.



-Then again that comes from some bozo who sells nitrogen generating equipment-and given that air is like 75% nitrogen in the first place, that claim is somewhat dubious-
The more I read about the less relevence I think it has for us regular folks, for airplanes and race cars there is a stronger argument for using it, but I burn through tires fast enough anyway that whats inside them really doesn't get a chance to come into play- I'll stick with air myself.....

 

last week

 

the place i get my motorcycle tires does this

 

airplanes and racecars use Nitrogen too. I personally think it's a gimmick.

 

It makes a little bit of sense...but the differences between air and N2 would be so minimal that I can't see it keeping tires from deflating at about the same speed. To do that you'd need a gas that was a larger molecule...maybe CO2 filled will be the next thing hahaha...hey, and since our cars all generate a bunch of CO2, it would be sort of like recycling hahahaha.

 

I think they mentioned this on Speed's coverage of F1, also. Tom and Ray Magliozzi (aka Click and Clack, the Tappet Brothers, aka Car Talk) has a blurb about the use of nitrogen for inflating tires although there's an error confusing F1 cars with IRL cars.

Bottles of Motul RBF 600 brake fluid is topped off with nitrogen instead of air so as not to introduce moisture.

--
0==WW==0
"…axles of evil…" - george w. bush

 

I'm a nerd...so I did a little research.
Compressed air:
78%Nitrogen, 21%Oxygen, 0.8%Argon, 0.2%Everything else
So basically the argument is pure N2 vs N2/O2 mix (the trace gasses don't contribute enough to matter).

The volume of a N2 is 17.3cm3/mol
The volume of an O2 is 10.52cm3/mol
The difference may be enough to effect the time it takes for a tire to flatten under normal use, although I would like to see data about it.
(NOTE:some websites selling the N2 tire-fill theory claim that N2 is more massive, therefore it won't leak...when in fact O2 is more massive, but slightly smaller in volume. This makes me think that the people trying to sell this idea are not scientists and probably don't really know if it's better or not. And I could not find on any site any data about how long it takes a tire to loose air w/ N2 vs air.)

Another argument for using pure N2 in a tire is the oxidative qualities of oxygen. Oxygen does degrade everything; however, when was the last time your tires wore out because they developed a crack from the inside? Never...we wear out the outer tread WAY before rubber starts to degrade from internal oxygen. (Furthermore, sunlight combined with oxygen would do severe damage to the outside of the tire far before internal oxygen would do anything, for cars that aren't driven much).

But race cars and airplanes DO use N2 in their tires. The reason? The tires in those applications get hot enough to catch on fire, and using N2 limits the amount of O2 near by (since O2 is required for fire).

Bottome line: If you race a lot, and your tires get hot enough to self-ignite (probably noone but NASCAR and F1/Champcar guys), use Nitrogen. Otherwise, I assume it's a waste of money. If it does not cost anymore than air, then it does not matter which you use.

Edit: I forgot to mention the water vapor issue (which is probably the best reason to use N2). This is another big reason race cars use N2. (Water vopor changes volume a lot with temp change around ambiant temperatures because it's so close to it's evap/condesation point). But for normal driving in a normal car, this should not be an issue.