Tread Design for Heavy-Load Transport Vehicles

A tire tread intended to be fitted on heavy vehicles, comprising a plurality of elements in relief, this tread being divided in the axial direction into three parts, a central part and axially on either side a first edge part and a second edge part,

• the central part of the tread has a width Lc which is determined as the width of the region of the tread the contact patch of which has, in a load condition equal to 0.40 times the E.T.R.T.O. rated load and at E.T.R.T.O. rated pressure, between the maximum length of contact and the minimum length of contact, a difference at most equal to 0.5% of the total width W of the contact patch,
• the first and the second edge parts comprising elements in relief arranged at a pitch Pe corresponding to the average circumference of the edge in question and measured over the median part of said edge at the radially outermost point when the tire is mounted on its rated rim and inflated to its rated pressure divided by the number of elements in relief on the edge in question,
• the elements in relief of each edge part having a line of leading ridges and a line of trailing ridges,
• wherein the lines of ridges of the elements in relief of the first edge part have profiles which cannot be superposed on the profiles of the lines of ridges of the elements in relief of the second edge part, be it by central symmetry in the case of a non-directional tread or by axial symmetry in the case of a directional tread,
• wherein the difference between the absolute value of the angle of the average direction of each line of ridges of an element in relief of the first edge part and each of the absolute values of the angles of the average directions of the lines of ridges of each element in relief of the second edge part is at least equal to 10 degrees and at most equal to 20 degrees, and
• wherein the total contact surface of the elements in relief of the edge parts passing through a window of a circumferential length equal to the pitch Pe of the elements in relief of the edge parts is substantially constant in that the relative deviation between the minimum value and the maximum value of the total surface on the ground is at most 5%, this total contact surface of the elements in relief being equal to the total of the contact surfaces of the elements in relief of the first and second edge parts.