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Re: [Phys-l] N2 vs air in your tires?



On 10/03/2006 11:34 AM, Bob Sciamanda wrote:
May I provoke a discussion regarding the current touting of using Nitrogen
(instead of air) in your car tires?
What can we say about the practical advantages/disadvantages of N2 vs air?

This was discussed in some detail on the chemed-l list not too long ago.
Here's what I got out of the discussion:

As for _car_ tires, it's mostly a scam, AFAICT.

Reportedly N2 diffuses through rubber more slowly than O2 does, but both
diffuse so slowly that it's not a significant issue.

At ordinary temperatures, the reactivity of O2 isn't a significant issue.

For _airliners_ the use of N2 is regulatory. They're worried about fire
in panic-stop situations. But keep in mind that panic-stopping a few
hundred tons of airliner in a short distance on rather small tires is
quite different from anything you're likely to do with your car. N2
is not required for light aircraft.

Perhaps the closest the N2 "service" comes to providing real value has
to do with moisture. In a typical shop, compressed air is derived from
the atmosphere, with no particular effort to dewater it. In contrast,
nitrogen comes from a cylinder of dry nitrogen. Very, very dry nitrogen.
There is arguably an advantage to using dry nitrogen (or dry anything)
over non-dry anything else, because you don't want any appreciable
condensed moisture inside your tires.