| 摘要 |
A heavy duty pneumatic radial tire for use under a high speed and a high internal pressure, is disclosed, which comprises a plurality of carcass cord layers of which cords are arranged at an angle from 90 DEG to 75 DEG with respect to a circumferential direction of the tire. The cords are composed of fibers of an aromatic polyamide having not less than 80 mole % of a repeating unit expressed by the following formula: -NH-Ar1-NHCO-Ar2-CO- in which Ar1 and Ar2 denote at least one kind of an aromatic residue selected from: <IMAGE> +TR <IMAGE> Elongation En (%) of the aromatic polyamide fibers constituting the respective plies meets the following inequation: En-1+0.2</=En</=En-1+2.0 in which En is an elongation (%) of the n-th layer of the carcass cord layers, provided that the carcass cord layers are taken as 1st ply, 2nd ply, 3rd ply, . . . , n-th ply from the inner liner side in which n is an integer of 2 or more, and E1 may take any arbitrary value.
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