A pneumatic tire (10) having a tread portion (11) including a continuous mid-circumferential rib (28), and primary grooves (22,23) on each side of said rib that form an "S" or "Z" shaped configuration diagonally across the tread portion. A plurality of blades (30) are arranged to extend in circumferentially spaced blade paths (34) across the tread. The blade paths (34) extend substantially continuously between the tread edges (12,13) in a diagonally opposite direction to the primary grooves (22,23) such that each primary groove is intersected by a plurality of blade paths.