Convertible tread for a radial truck or trailer tire

A radial ply pneumatic tire for trucks and trailers having a tread with a non-skid depth D, at least three circumferential grooves extending circumferentially to divide the tread into at least four parts, lateral grooves extending across the at least four parts of the tread to form at least four rows of circumferentially separated blocks, including two shoulder rows, and at least two central rows, each block having a radially outer surface, the tire characterized by:

• the circumferential grooves having a first average groove width W1 for a depth between the radially outer surface of the adjacent blocks and a groove depth that is less than 60% of the non-skid depth D, the circumferential grooves having a second average groove width W2 at the groove depth that is less than 60% of the non-skid depth D, the second average groove width W2 being less than 50% of the first average groove width W1, the lateral grooves in each shoulder row having a first average groove width W3 and a groove depth of less than 60% of the non-skid depth D, the lateral grooves in the central rows having a first average length of L1 for a depth between the radially outer surface of the adjacent blocks and a groove depth that is less than 60% of the non-skid depth D, the lateral grooves in the central rows having a second average length L2 at the groove depth that is less than 60% of the non-skid depth D, the second average length L2 being greater than the first average length L1, the lateral grooves in the central rows having a second average groove width W4 at the groove depth that is less than 60% of the non-skid depth D, and
• wherein the second average groove width W2 of the circumferential grooves and the second average groove width W4 of the lateral grooves in the central rows occur at the same radial depth, the lateral grooves in the shoulder rows cease at the same depth that the second groove widths W2 and W4 occur when the tread is worn to the location at which widths W2 and W4 occur, thereby forming two shoulder ribs and at least two central rows of circumferentially spaced blocks.