Pneumatic tire with tread having bottom raising portions

A pneumatic tire having a tread surface that has a specified tire rotation direction, shoulder blocks being defined on a shoulder side of the tread surface by lateral grooves extending in a widthwise direction of the tire beyond a ground contact end of the tire and having a depth within a range of 4 mm to 7 mm, the shoulder blocks being arranged in a circumferential direction of the tire, wherein a first bottom-raising portion having a height which is 30% to 70% of a depth of the lateral groove from a bottom thereof is provided on the bottom of a portion of only every other lateral groove of the lateral grooves such that the bottom of each of the every other lateral grooves has a step profile and so as to connect two shoulder blocks adjacent in the circumferential direction of the tire by the first bottom-raising portion, the every other lateral groove portion being outward of the ground contact end of the tire in the widthwise direction of the tire,

• a main groove extending in the circumferential direction of the tire is provided on an equatorial plane of the tire in the tread surface;
• the lateral grooves extending in the widthwise direction of the tire beyond a ground contact end of the tire are further provided on another shoulder side of the tread surface, right and left lateral grooves on the shoulder sides being disposed at prescribed intervals in the circumferential direction of the tire, the right and left lateral grooves extending from the main groove toward opposite sides of the tire in the widthwise direction of the tire beyond ground contact ends of the tire in an inclined manner toward a reverse rotation direction of the tire;
• right and left inclination grooves are provided on opposite sides of the main groove at prescribed intervals in the circumferential direction of the tire, the right and left inclination grooves extending across the right and left lateral grooves in such an inclined manner with respect to the circumferential direction of the tire that tire reverse rotation direction sides of the inclination grooves are more away from the main groove than tire rotation direction sides of the inclination grooves;
• center blocks are defined on the opposite sides of the main groove by the main groove, the right and left lateral grooves and the right and left inclination grooves;
• the shoulder blocks are defined on the opposite shoulder sides of the tread surface by the right and left lateral grooves and the right and left inclination grooves;
• the right and left inclination grooves are disposed at symmetrical positions with respect to the equatorial plane of the tire;
• the center blocks comprise right and left first center blocks defined by tire rotation direction side portions of the right and left inclination grooves, the main groove and the right and left lateral grooves, and right and left second center blocks defined by tire reverse rotation direction side portions of the right and left inclination grooves, the main groove and the right and left lateral grooves, a circumferential length of each second center block being greater than a circumferential length of each first center block;
• and
• a second bottom-raising portion is provided on a bottom of the main groove between each two first center blocks standing on the opposite sides of the main groove so as to connect the two first center blocks by the second bottom-raising portion, and
• wherein the pneumatic tire is a tire for a racing cart.