Patent ID: 7573376

Claim:
A method for indicating abnormality in tire air-pressure of a tire mounted on a vehicle, while preventing an erroneous indication of abnormality in tire air-pressure due to a new tire mounted on the vehicle, the method comprising the steps of: comparing rotational velocities of each tire to thereby detect an abnormal tire air pressure in one of the tires when the comparison yields a value equaling or exceeding a first threshold value; and providing an indication of the detected abnormal tire air pressure; and wherein the method further includes the steps of: calculating a first determinate value by comparing rotational speeds of a first two pairs of tires from among the pairs of tires mounted at (1) diagonal positions on the vehicle, (2) left and right sides of the vehicle and (3) front and rear axles of the vehicle; calculating a second determinate value by comparing rotational speeds of a second two pairs of tires that is different from the first two pairs of tires; calculating a third determinate value by comparing rotational speeds of a third two pairs of tires that is different from each of the first two pairs of tires and the second two pair of tires; detecting whether a new tire is mounted on the vehicle by comparing a difference in the determinate values with a second threshold value, before and after enlargement of the diameter of the new tire, based on the phenomenon that a diameter of a new tire on a vehicle enlarges after running; and adjusting the first threshold value when it is detected that a new tire has been mounted on the vehicle.