IN-SERVICE EVALUATION OF NITROGEN INFLATION OF TIRES

The use of nitrogen gas inflation for tires in severe service conditions is known.  A variety of benefits have been claimed for use in passenger car tires.  In order to study specific claims, the use of dry air and dry pure nitrogen inflation was tested in both laboratory testing and evaluations under in-service conditions. 
It is shown from laboratory experiments that the primary benefit of using nitrogen as the filling gas is to reduce the tire inflation pressure retention (Tire IPR) monthly loss rate values.  Other claimed benefits such as cooler operating temperature and lower rolling resistance are found to be the primary result of tire inflation pressure, with the type of filling gas being statistically insignificant. 
An in-service evaluation of four tire types on different vehicles also shows that the benefit of nitrogen gas inflation is to reduce the actual Tire IPR loss rates measured on the vehicle.  A small measurable benefit is observed for vehicle fuel economy, but is a primary effect of inflation pressure with inflation gas again being statistically insignificant.