Patent ID: 7392832

Claim:
A pneumatic tire comprising: a carcass having an axis of rotation; and a tread disposed radially outward of said carcass, said tread including an equatorial plane bisecting said tread perpendicular to said axis of rotation, a plurality of lateral grooves intersecting said equatorial plane, first and second ribs extending circumferentially about the tread so as to intersect said plurality of lateral grooves, a first plurality of tread blocks defining said first rib, and a second plurality of tread blocks defining said second rib; wherein a first tread block in said first rib and a second tread block in said second rib each include a road-contacting surface, a first wall extending from said road-contacting surface and bordering one of said lateral grooves, and a second wall extending from said road-contacting surface and bordering another one of said lateral grooves, each of said first walls having a first angular orientation relative to said equatorial plane at a first groove depth at or below the road-contacting surface and a second angular orientation relative to said equatorial plane at a second groove depth smaller than the first groove depth, each of said first walls having a spiral angle equal to the difference between the first and second angular orientations, the spiral angle of said first wall of said first tread block differing from the spiral angle of said first wall of said second tread block such that said lateral groove bordered by said first walls defines a non-linear path across said first and second ribs at the first groove depth and a substantially linear path across said first and second ribs at the second groove depth; wherein each of said tread blocks in said first rib has a first cross-sectional profile in a direction orthogonal to said axis of rotation at the first groove depth and a second cross-sectional profile in a direction orthogonal to said axis of rotation at the second groove depth, said first cross-sectional profile being a trapezoid and second cross-sectional profile being a parallelogram.