Heavy-duty radial tire for use on and off the road

Claim 1

A radial tire for heavy-duty vehicles comprising a tread having a central portion and two lateral portions, the central portion being formed with at least one circumferential rib and at least two circumferential grooves, the circumferential rib having a wall in common with each circumferential groove, and each lateral portion being formed with a substantially continuous circumferential zigzag rib and with alternating transverse grooves and blocks, each of said substantially continuous circumferential zigzag ribs defining angles that are alternately reentrant and salient, the transverse grooves forming extensions, in a direction towards the nearer edge of the tread, of the reentrant angles of the substantially continuous circumferential zigzag rib, the transverse blocks (a) forming extensions, in a direction towards the nearer edge of the tread, of the salient angles of the substantially continuous circumferential zigzag rib, (b) being contiguous with the substantially continuous circumferential zigzag, (c) alternately terminating at greater and lesser distances from the median plane of the tire, and (d) having a wall in common with the adjacent transverse grooves, the common walls of the transverse grooves and blocks having an inclination with respect to the normal to the tread surface that is greater than are the inclinations with respect to the normal to the tread surface of the common walls of the circumferential rib and circumferential grooves, the transverse grooves having at every level a greater width than the circumferential grooves have at the same level the total area of the substantially continuous circumferential zigzag ribs and blocks exceeding the total area of the circumferential rib or ribs in the central portion, the blocks having, in the circumferential and transverse directions, dimensions that exceed the width of the circumferential rib or ribs in the central portion, the transverse grooves having an angular course and perimeter, and the common walls of the transverse grooves and blocks having an inclination of 20* to 30* with respect to the normal to the tread surface.