A method for detecting decrease in tire air-pressure including the steps
of: detecting rotational information of the respective tires; storing
rotational information; detecting whether the vehicle is running on a flat
road or not; detecting whether the vehicle is accelerating or
decelerating; comparing rotational information of both front wheels with
rotational information of both rear wheels when it has been determined
that the vehicle is running on a flat road and that the vehicle is neither
accelerating nor decelerating; and judging simultaneous decompression of
both front wheel tires or simultaneous decompression of both rear wheel
tires on the basis of a relationship between a value obtained through
comparison of the rotational information of both front wheels and both
rear wheels and a specified threshold. It is possible to judge
simultaneous decompression of both front wheel tires or both rear wheel
tires when employing the present invention.
