A pneumatic radial tire for passenger cars having a plurality of grooves formed in the tread and extending at least circumferentially of the tire, the tread being provided with two belt plies therein in such a manner that their belt cords extend in a crisscross pattern. The grooves have a depth in the range of 6.0 to 8.5 mm, with the thickness of the under-groove rubber layer from the bottom of the grooves to the outer belt ply being fixed within the range of 0.5 to 2.0 mm. The belt plies are placed one over another with the both edge portions left unfolded. At least one of the plies is made from aramid fiber cords and at least the both edge portions of the belt plies are covered with at least one belt cover ply which has a cord angle of no greater than 30 deg with respect to the circumference of the tire. The belt cover ply is made of organic fiber cords no larger than 0.7 mm in diameter at a picking density of 35 to 90 percent.