Abstract: Determining the rate of change of fluid pressure in a tire comprises mounting the tire in an inflated condition. A tire pressure sensor senses fluid pressure in the tire and generates an electrical signal in proportion to the fluid pressure sensed in the tire. A temperature sensor senses the temperature adjacent the tire and generates an electrical signal in proportion to the temperature sensed adjacent the tire. A data acquisition system is in electrical communication with the sensors. The data acquisition system receives the electrical signals from the respective sensors at a substantially simulatneously time and converts the electrical signals into digital information. An electronic digital computer is an electrical communication with the data acquisition system for receiving the digital information and for calculating a value representative of a corrected pressure in the tire as a function of the digital information received. A plurality of the corrected pressure values are stored.