PURPOSE: To realize a radial tire with increased high-speed durability by minimizing the difference between the center stretch of an auxiliary belt layer and the strength of a shoulder part and improving a function to improve the thermal contraction of the shoulder part and in turn, restrain the lifting of a belt layer.

CONSTITUTION: A plurality of belt plies consisting of inorganic and organic fiber cords with an angle of 10°W40° in a peripheral direction on the external periphery of a belt drum in a non-spread diameter, are overlapped to form a cylindrical belt layer B. The belt drum 1 is diametrally expanded and deformed so that its axial cross-section is the same or almost the same as the final finished shape in a die of an auxiliary belt layer BR, or in concrete terms, that its absolute value of the difference between the center stretch and the shoulder stretch of the auxiliary belt layer is 0W2%, and subsequently, the belt drum 1 is in a projected form. Then the auxiliary belt layer BR consisting of organic fiber cords with an angle of 0°W5° in a peripheral direction is formed on the outer side in a radial direction of a belt layer B on the belt drum deformed as described above. Next, a tread rubber layer T is wound around the outer side in a radial direction of the auxiliary belt layer to form an integrally built belt/tread assembly.