[Ashrod]

From my experience with racing go karts where the tires have to reach an optimum operating tempature of 165* F, when I ran tires with air or nitrogen they both reacted the same as far as how much air pressure was increased and it also took the same amount of laps to build the same heat and air pressure!!! With all that being said, I would look into foam filling the tires to achieve what you want!!! Also my wife's new nissan cube dropped air pressure from the recommended pressure of 44 psi to an average of 20 psi when the cold weather set in, and they are nitrogen filled also!!! Hope this helps!!!