Serrated groove sides in a tire

A tread portion for a motor vehicle tire having a carcass and attached side walls, said tread portion-having opposite sides and including

• a plurality of block-shaped tread elements arranged in a series of rows around the tread portion, the tread elements having an outer surface and a plurality of side surfaces and being spaced apart circumferentially and transversely about the tire tread portion to form a tread thereon,
• selected ones of said tread elements defining between them a plurality of peripheral grooves extending around and forming the outer surface of said tread portion,
• each groove having a bottom portion comprising a groove base and groove sides extending from the outer surface of said tread portion into said tread to the groove base within the tread portion,
• the tread elements on opposite sides of a respective groove above said bottom portion including separate upper side surface portions on one side of said groove extending upward and away from an upper edge of the groove bottom portion to said tread surface,
• a majority of said selected upper side surface portions having a set of serrations thereon extending inward of said outer surface and terminating at their junction with the upper edge of said bottom portion of the groove,
• said set of serrations covering the selected upper side portions and extending inward of the outer surface to the junction of said serrations with the bottom portion of the groove presenting a first traction surface of substantially greater surface area than presented by a comparable but non-serrated upper side surface portion of said tread elements,
• said traction surface sloping inward of the outer surface at an angle in the order of 30° to 45° with respect to a radial plane and intersecting the side of said bottom portion of the groove above said base of said groove at about 60% of the total groove depth to form a wider upper part of said groove, whereby the width of the groove diminishes in width radially inward toward, and short of, said base of said groove and the traction surface is predominantly within the upper part of the groove wherein the side of said bottom portion is inclined with respect to the radial plane at an angle smaller than the angle at which the traction surface slopes.

A motor vehicle tire having a carcass including side walls and a tread portion on the periphery of said tire carcass extending between the side walls, said tread portion comprising a relatively thick layer of elastomeric material having an outer surface and a pattern of relieved areas in said layer defining a plurality of block-shaped spaced apart tread elements to form a tread surface which will be in rolling contact with roadway surfaces,

• said tread elements being arranged in rows extending circumferentially about the tire tread portion,
• selected tread elements defining between them a plurality of peripheral and transverse grooves in the tread, each groove having a bottom portion comprising a groove base and groove sides extending upward from the groove base at an acute angle for about 40% of the groove depth, whereby the tread elements on opposite sides of a respective groove form discontinuous separate upper side walls of said groove,
• the upper portions of said selected tread elements having serrations extending inward and downward at an angle to said tread surface, said serrations presenting a traction surface sloping inward from the tread at an angle in the order of 30° to 45° with respect to a radial plane and terminating above the bottom of said groove at about 60% of the groove depth to form an upper part of said groove, whereby the groove diminishes in width radially inward toward said bottom of said groove wherein the side of said bottom portion is inclined with respect to the radial plane at an angle smaller than the angle at which the traction surface slopes.