Abstract: A heavy duty pneumatic radial tire is disclosed, which comprises a single carcass ply having aromatic polyamide fiber cords at a cord angle of about 90.degree. relative to a tire equatorial plane, a pair of bead cores, and first and second reinforcing layers successively laminated axially outside turn-up portions of the carcass ply. A height of the turn-up portion is from 0.075 to 0.16 time that of the carcass ply in a tire section. The first reinforcing layer comprises steel cords arranged obliquely to the carcass ply cords, and has a radially outer end higher than an end of the turn-up portion. The following relation exists among a.sub.1, d.sub.1, a.sub.2, d.sub.2, T.sub.1 and T.sub.2 : ##EQU1## in which a1, d.sub.1, a.sub.2, d.sub.2, T.sub.1, and T.sub.