Patent ID: 7543616

Claim:
A heavy duty tire comprising a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion, and a belt layer disposed inside the tread portion and outside the carcass, wherein the belt layer includes a carcass-side first belt ply and a second belt ply disposed outside thereof, and when the tread thickness between the profile line of the tread surface and the second belt ply is defined as T, a tread thickness Ty in a region Y the boundaries of which are separated from the tire equator C by distances of 0.5 and 0.7 times the half of the ground-contact width of the tread is set in the range of 1.00 to 1.05 times the tread thickness Tc at a position of the tire equator C, and the tread thickness Tb at the position of the outer end of the second belt ply is set in a range of 0.98 to 1.03 times the tread thickness Tc, the tread portion is divided by three longitudinal main grooves extending in a circumferential direction of the tire into inner rib-like land portions J 1 on each side of the tire equator and ground-contact edge-side outer rib-like land portions J 2 , and each longitudinal main groove between the inner rib-like land portion J 1 and the outer rib-like land portion J 2 is located in said region Y, in a regular ground-contact state in which the tire is mounted on the regular rim, the regular internal pressure is charged into the tire and the normal load is applied to the tire, a ratio P 1 e /P 1 c between a total sum of ground-contact forces P 1 c applied to a tire equator-side half region J 1 c in the inner rib-like land portion J 1 and a total sum of ground-contact forces P 1 e applied to a ground-contact edge-side half region J 1 e is set in a range of 0.8 to 1.0, a ratio P 2 c /P 1 e between the total sum of ground-contact forces P 1 e and a total sum of ground-contact forces P 2 c applied to a tire equator side half region J 2 c in the outer rib-like land portion J 2 is set in a range of 0.8 to 1.0, a ratio P 2 e /P 2 c between the total sum of ground-contact forces P 2 c and a total sum of ground-contact forces P 2 e applied to a ground-contact edge side half region J 2 e in the outer rib-like land portion J 2 is set in a range of 0.6 to 1.0, wherein the total sums P 1 c , P 1 e , P 2 c and P 2 e have a relationship of P 1 c >P 1 e >P 2 c >P 2 e , and a ratio P 2 e /P 1 c between the total sum of ground-contact forces P 1 c and the total sum of ground-contact forces P 2 e is set in a range of 0,4 to 0.9.