Pneumatic tire, mold including vent grooves, and method

A mould for vulcanizing a pneumatic tire,

• the pneumatic tire comprising
• a tread portion having a tread surface, the tread surface having a radius of curvature of 400 to 1500 mm,
• a pair of buttress portions, and
• a pair of shoulder portions between the tread portion and buttress portions, the shoulder portions tapered axially outwards at an angle of 30 to 60 degrees with respect to an axis of the tire and provided with circumferentially extending narrow grooves,
• the mould comprising
• a tread molding face having axial edges for forming the tread surface of the tire,
• a pair of buttress molding faces each having a radially outer edge for forming the buttress portions of the tire,
• a pair of tapered shoulder molding faces for forming the shoulder portions of the tire, each extending between one of the axial edges of the tread molding face and the radially outer edge of one of the buttress molding faces,
• the tread molding face provided with vent holes,
• each of the shoulder molding faces provided with a protrusion for forming one of the circumferentially extending narrow grooves of the tire,
• the protrusion provided with slits for forming thin partition walls in each of the narrow grooves of the tire,
• vent grooves each extending from and positioned over one of the slits in the shoulder molding face into the tread molding face for forming a rib on one of the partition walls which protrudes from the tread surface and the narrow groove,
• each said vent groove having a depth of from 0.5 to 2.0 mm and a width of more than 0.5 mm but not more than 2.0 mm, and
• each said slit having a width of from 0.5 to 2.0 mm.