[s-cars] Nitrogen in tires?

Robert Myers robert at s-cars.org
Sun Apr 28 14:01:28 EDT 2002

At 12:41 PM 4/28/02, Charlie Smith wrote:

>Earlier, ccohen5 wrote:
> >
> > How does one get the stuff into the tires without mixing it with
> air.  Or is
> > it acceptable to have a N concentration but not pure N except for those F1
> > folks who probably fill their tires in a vacuum chamber??
>Use of nitrogen in tires is a common practice with racers, because
>tire pressure is critical for best handling.  They carry a pressure
>bottle, similar to an oxygen tank used with welders.  To set up
>something like this, you'll need a high pressure regulator just
>like on a welding tank.
>After installation, inflate the tire and deflate it once,
>then inflate it again.  That gets rid of most of the air.

That would pretty much take care of it.  Not 100% but well toward 100%

>With a race tire, the sidewalls are very thin and flexible,
>so one can 'squish' the tire and get most of the air-nitrogen
>out of it before the second filling.  Since race tires leak
>like crazy, subsequent fillings will have even less air in
>them.  Figure, this will greatly reduce the pressure change with
>temperature change, and that's what's important.

I'm sure you are correct about the practice, Charlie, but air (primarily a
mixture of 80% N2 & 20% O2) will obey exactly the same gas laws as will
"pure" N2.  This makes no sense as an argument for using only N2 to inflate
the tires.  Perhaps there is some valid reason for its use but this one
ain't it.  Perhaps the convenience of using a bottle of gas rather than
having to schlep around a compressor might have something to do with it?

>Also figure - race tires are more sensitive to pressure being
>exactly spot-on.  Plus, the benefits of nitrogen allow the pressure
>to be right even on the first lap before the tires are fully heated up.

Again, Charlie, the tire pressure will change essentially the same way on
heating whether air or N2 is used.  This is a nonsense argument.  I'm sure
you have heard it expressed this way but it's still nonsense.

>     - Charlie
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  Robert L. Myers   304-574-2372
  Rt. 4, Box 57,  Fayetteville, WV 25840 USA   WV tag Q SHIP
  '95 urS6  Cashmere Grey - der Wunderwagen    ICQ 22170244

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