Patent ID: 7233238

Claim:
Tires attached to wheels of a vehicle and monitored by a tire air-pressure alarming device which is incorporated in the vehicle and comprises wheel speed detection means for detecting wheel speeds of the wheels of the vehicle; judgement value deriving means for deriving a judgment value based on the wheel speeds detected by the wheel speed detection means; air-pressure drop judging means for judging the occurrence of air-pressure drop of the tires constituting the wheels, based on the judgment value derived by the judgment value deriving means; and alarming means for raising an alarm when the occurrence of the air-pressure drop of the tires to a judgment pressure is judged by the air-pressure drop judging means; wherein the wheel speed detection means pick up the rotations of the wheels; wherein each of the tires is selected to have a controlled property value which falls within a predetermined range when detected in a predetermined state that at least one of vehicle speed, wheel load and air pressure is varied from a reference state; and wherein the performance of the tire air-pressure alarming device in judging the air-pressure drop of the tires by the air-pressure drop judging means is standardized by using the tires each of which has been selected to have the controlled property value and by correlating the controlled property values of the tires with the judgment value.