The partial pressure of nitrogen in the atmosphere is 70+ %. You aren't diluting much if you have to add a few psi. 

-craig

On Mar 10, 2012, at 5:07 PM, george jannini <georgejoann@GMAIL.COM> wrote:

>   Hell why not helium for lower rolling resistance?  Or hydrogen, even
> lighter.  This is my Vanagon, I've named it Hindenberg...
> 
> George/ATL