A method for detecting decrease in tire air-pressure in which decrease in
internal pressure of a tire is detected on the basis of rotational
information obtained from tires attached to a vehicle. The method includes
the steps of; detecting and storing rotational information of the
respective tires; calculating and storing a slip rate; calculating and
storing a correction coefficient for correcting a difference in effective
rolling radii owing to initial differences between right and left front
tires, a correction coefficient between right and left rear tires and a
correction coefficient between front tires and rear tires; comparing a
correction coefficient between front tires and rear tires with a
correction coefficient between the front tires and the rear tires
preliminarily obtained when at normal internal pressure; and judging
simultaneous decompression of two wheel tires of both front wheels or
simultaneous decompression of two wheel tires of both rear wheels on the
basis of a relationship between a value obtained through comparison of the
two correction coefficients and a specified threshold.
