A heavy duty radial tyre having an improved bead structure to be mounted on a 15 degree drop centre rim is disclosed. When the tyre is mounted on its rim and inflated to 0.5 ksc but not loaded, the inside diameter BC of the bead cores (6) at the radially innermost point thereof is set to being not more than the diameter BT at the heel point of the bead portions. In a demounted state the bead bottom is tapered towards the axial inside of the tyre at an angle &thetas; of from 1.0 to 1.9 times the angle alpha of the tapered bead seat of the rim. <IMAGE>
