A tire includes a pair of sidewalls extending from a respective bead area to a tread. The tread is formed with a plurality of tread elements and a radially outer surface. A sensor unit is mounted to the tire and includes a pair of electrical contacts. The tread wear sensor plug includes a cylindrical projection extending through an opening formed in one of the tread elements, a flange, and a wire including proximal ends disposed in the flange and a distal end near a radially outer surface of the projection. An electrical circuit is formed by each proximal end of the wire electrically contacting a respective one of the sensor unit electrical contacts. When the tread element and the cylindrical projection wear down to the distal end of the wire, the wire and the circuit break. A notice is transmitted by the sensor unit when the circuit breaks.