I believe what the process is is that you fill with nitrogen then deflate
and refill.  That increases the %of N in the tire since pulling a vacuum
isn't practicable.

Sent from my iPhone

> On Oct 17, 2015, at 7:07 PM, Angus Gordon <birdworks@GMAIL.COM> wrote:
>
> > Quick, someone do the math: after inflating a tire to, say, 40 psi by
> > adding nitrogen atop regular air at atmospheric pressure, what's our %
N?
> >
>
> Roughly 93%
>
>
>
> >> On 10/17/2015 02:57 PM, Max Wellhouse wrote:
> >> Eric:  I have a friend here in Cedar Falls Iowa that fills his tires
> >> exclusively with nitrogen.  He runs a really small tire mounting and
> >> balancing shop out of his garage and does mobile repairs as well.  He
> >> says that in order to mount tires and fill them with nitrogen, you
> >> have to make sure the bead sealing surface is absolutely pristine, so
> >> there's no chance of micro leaks from pitted sealing surfaces.  I
> >> think he charged like $10/tire to do the fill.  Not sure how he would
> >> evacuate the normal atmospheric air form the process, but I have used
> >> his services on my Vanco II Continentals mounted on Mercedes CLK
> >> forged aluminum rims(mounted on my 90 GL  BTW)  and they haven't lost
> >> 1 psi in like 4 years.  I think Tire Rack offers the service as well.
> >> NASCAR Racers use nitrogen     YMMV