Radial tyre for heavy duty vehicles

A radial ply tyre for heavy duty vehicles improved in bead durability, which has a bead reinforcing cord layer (5) having an axially inner portion (5A) extending along the inside of the carcass main portion, and an inner liner (6) which is provided with a middle portion (7C) which has a thickness which is gradually decreased radially outwardly, the heights (H7b, H7a) of the lower end (7b) and upper end (7a) of the middle portion (7C) are respectively not smaller than 1.2 and 1.4 times the height (H5a) of the upper edge (5a) of the axially inner portion of the reinforcing layer (5), the difference (Wd) in thickness (W7a) between the upper (7a) and lower ends (7b) of the middle portion (7C) is between 0.5 and 1.0 times the thickness (W7a) at the upper end (7a) of the middle portion (7C) and the thickness (W7c) at 90% of the height (H5a) of the upper edge (5a) of the axially inner portion (5A) of the reinforcing layer (5) is between 0.9 and 1.2 times the thickness (W7a) at the upper end (7a) of the middle portion (7C).