This invention is concerned with a radial tire, particularly a heavy duty radial tire aiming at the improvement of durability, and is characterized by rendering a ratio W2/W1 of width W1 of a belt layer located side a carcass to width W2 of the remaining belt layer in small slant belt layers arranged at a width corresponding to 0.25 0.50 times a tread width in a widthwise direction of the tire, whereby growth and progress of cracks in the vicinity of cord ends of cords used in the belt resulting in separation failure at widthwise ends of the belt are effectively prevented to overcome a weak point in the tread reinforcement of the radial tire.