Process for the determination of the tread depth of a tire and tire

Ferromagnetic particles(6) are located at various positions in raised blocks(5) of the tread strip(1) and produce electromagnetic or electrodynamic signals in a sensor(7) positioned just above the tread surface. Ferromagnetic particles(6) are located at various positions in raised blocks(5) of the tread strip(1) and produce electromagnetic or electrodynamic signals in a sensor(7) positioned just above the tread surface. Signals are fed from the sensor to an electronic analyzer which, depending on the type of signal, determines the amount of tread abrasion and on reaching a threshold value corresponding to the maximum permissible abrasion gives an indication to the driver. An Independent claim is also made for a tire employing the claimed tread depth measurement method and incorporating magnetically conductive particles in the form of spheres or small plates in the tread to form local points of measurement. Particles are located at different depths and are offset from each other in the axial or circumferential direction. Three or more particles are preferred at each measuring point. Within a circumferential row of raised blocks or strips there are two or more measuring points.