Pneumatic tire having bell shaped wide width main grooves

A pneumatic tire having a central region corresponding to TW110×35% and both shoulder regions when TW110 is a ground contact width of a tread in the tire mounted onto a rim of 7-5 inches under an internal pressure of 100 kPa and a load of 1078 N, in which no wide-width main groove continuously extending in a circumferential direction is existent in the shoulder regions, characterized in that a wide-width main groove extending straight in the circumferential direction and having a see-through width corresponding to 5-9% of TW110 and a groove depth corresponding to 65-90% of a rubber thickness of the tread is disposed on an equator of the tire and a plurality of bell-shaped wide-width main grooves each extended substantially bell-shapedly into both sides approximately centering on an equator of the tire are disposed in the tread to form a plurality of land parts each comprised of a center land portion, a shoulder land portion and a connecting land portion viewing from a front face of the tire in which an inclination angle with respect to the circumferential direction is 90-10° in the central region and 10-90° in the shoulder region and a groove width is 7-13% of TW110 and a groove depth is 65-90% of the rubber thickness of the tread, and an interval (d3) on the equator between the bell-shaped wide-width main grooves adjoining to each other in the circumferential direction is 4.0-5.5% of a tire peripheral length and a width (d4) of the connecting land portion at a position coming the bells-shaped wide-width main grooves closest to each other is not less than 1.5 mm, and a negative ratio at the central region is 55-65%;

• wherein the bell-shaped wide width main grooves are substantially symmetric with respect to the equatorial plane,
• wherein at least one sub-groove is arranged in the shoulder land portion formed in the shoulder region between the adjoining bell-shaped wide-width main grooves to render the shoulder land portion into a fork shape, in which a groove width is 30-65% of the width of the main groove and a groove depth is 40-100% of the depth of the main groove.