Patent attributes
A heavy duty tire having a bead wind structure and comprising a bead reinforcing layer 15 having a U-shaped cross section disposed in each bead portion 4, wherein the axially outer portion 15o of the bead reinforcing layer 15 and its radially outer end Pe are protected by an axially inner rubber 20 disposed between the carcass main portion 6a and the outer portion 15o and an axially outer rubber 30 disposed between the outer portion 15o and the axially outer surface TS of the tire, in which the inner rubber 20 includes a first low modulus rubber portion 21 having a complex elastic modulus of 3.0 to 6.0 MPa, the thickness Ti of the inner rubber 20 measured on a first base line X1 drawn from the radially outer end Pe at right angles to the carcass main portion 6a is from 7.0 to 13.0 mm and the ti/Ti ratio of a thickness ti of the first low modulus rubber portion 21 on the first base line X1 to the thickness Ti is at least 0.9; and in which the outer rubber 30 includes a second low modulus rubber portion 31 having a complex elastic modulus of 3.0 to 6.0 MPa, the thickness To of the outer rubber 30 measured on a second base line X2 drawn from the radially outer end Pe at right angles to the axially outer surface TS of the tire is from 5.0 to 11.0 mm and the to/To ratio of a thickness “to” of the second low modulus rubber portion 31 on the second base line X2 to the thickness To is at least 0.4. The weight of the bead portion can be reduced while maintaining the bead durability.
