Heavy duty radial tire with at least four steel cord layers

A heavy duty radial tire comprising:

• a belt layer assembly which is provided at a crown portion of a carcass extending in a toroidal shape, said belt layer assembly being formed of at least four layers which are formed from steel cords, wherein the layers of said belt layer assembly are divided into two groups, a first group of outer layers positioned at an outer side in a radial direction of said radial tire and a second group of inner layers positioned at an inner side in the radial direction of said radial tire, the cross sectional areas of the steel cords of at least one layer of the first group of outer layers being greater than the cross sectional areas of the steel cords of the second group of inner layers, the cross-sectional areas of the steel cords of each of the first group of outer layers and each of the second group of inner layers being between 3.80 mm.sup.2 and 8.55 mm.sup.2,
• wherein ratios I/A of cross sectional secondary moments I and cross sectional areas A of the steel cords of at least one layer of the first group of outer layers and the second group of inner layers are greater than or equal to 4.5.times.10.sup.-3 mm.sup.2,
• wherein, when the filament diameter of a steel cord is d,
• I=.SIGMA. ((.pi./64)d.sup.4))
• and
• A=.SIGMA..pi. (d/2).sup.2.
• 2.