Dry air is expensive to generate?   Funny, it's 'generated' in pneumatic equipment all over North America on a daily basis.  

The pneumatic doors at your local food plant or airport aren't powered by nitrogen gas - dry air is much cheaper!  Another 'justification' for charging you $10 for nitrogen that costs 5 cents - and replaces 2 cents worth of air.

James (who teaches pneumatics as part of his course load)
Ottawa, ON

> Date: Tue, 20 Oct 2015 11:16:53 -0600
> From: jondvo@GMAIL.COM
> Subject: Re: Nytrogen and tires
> To: vanagon@GERRY.VANAGON.COM
> 
> The reason Nitrogen is used is because it eliminates water vapor issues
> with freezing. Nitrogen is free of water vapor and "dry" air is as
> expensive to generate.
> 
> On 10/20/2015 9:55 AM, Angus Gordon wrote:
> >> PV = nRT ( T in Kelvin)
> >> It's all you need to know Angus. For tires, balloons, business meetings :)
> >>
> > I knew I'd been missing something. It's all about hot air, says Alistair...
> >
> > Angus
> >
> >
> >>
> >>> On Oct 19, 2015, at 3:53 PM, Angus Gordon <birdworks@GMAIL.COM> wrote:
> >>>
> >>> Thanks David, I've been using a rule of thumb of 1% per 5F for a long time but I don't know where it came from. Michelin perhaps. Normally I only use it to overinflate when headed to a cold destination. Kept me out of the weeds so far...
> >>>
> >>> Angus
> >>>
> >>>
> >>>> On Oct 19, 2015, at 3:46 PM, David Beierl <dbeierl@attglobal.net> wrote:
> >>>>
> >>>> At 11:19 PM 10/17/2015, Angus Gordon wrote:
> >>>>> I have experience with nitrogen filled tires on aircraft and can tell you that it certainly doesn't negate pressure changes with temperature. That's still something we deal with. I don't see any real value in using nitrogen in car tires.
> >>>> I believe pressure change as a percentage per degree will be essentially the same no matter what gas or combination of gases is used to fill a tire.  It amounts to roughly one psi per ten degrees Fahrenheit for tires at ordinary pressures and temperatures.
> >>>>
> >>>> Yrs,
> >>>> d