An apparatus for alarming decrease in tyre air-pressure on the basis of a rotational information obtained by tyres attached to a four-wheeled vehicle, comprising rotational information detecting means; memory means for storing the rotational information; c...

A method for alarming decrease in tyre air-pressure for judging a decrease in internal pressure of a tyre (W1...W4) attached to a four-wheeled vehicle and for accordingly generating an alarm. A threshold (DEL) for judging decompression is set to be larger ...