Method of detecting a deflated tire on a vehicle

A method of detecting a partially deflated tire on a vehicle having four tires each mounted on a wheel, each wheel having a signal generator for producing a series of digital signals or pulses spaced apart by equal increments from angular rotation of the respective tire and wheel assembly, the steps comprising:

• calculating vehicle speed from one of the series of signals or pulses produced by the signal generator for a reference tire selected from among the four tires;
• selecting an appropriate interval for deflation detection from the calculated vehicle speed;
• measuring a speed of rotation signal for each of the four wheels during said interval;
• storing the measured speeds;
• repeating the measuring step for at least three consecutive successive equal intervals and storing the results of each repetition;
• averaging the stored speeds to produce an average speed signal for each wheel;
• processing the four signals in a processing unit which subtracts the sum of the signals from one pair of diagonally opposite wheels from the sum of the signals from the other pair of diagonally opposite wheels;
• sensing when the magnitude of the result of said processing steps is in the range of between 0.05% and 0.6% of the mean of the two sums;
• and
• when the mean of the sums in within the prescribed range, operating a warning device to indicate that a tire is partially or completely deflated.