An improved radial ply tire

An improved radial ply pneumatic tire 30 is described. The improved tire 30 has a first annular surface 23 located between the heel 22B and toe 22A of each bead 33,53,63 and a second surface 24 extending radially outwardly from the bead heel 22B. The first surface 23 is designed to be in contact with the bead seat 42 of the design rim 40 when the tire 30 is mounted and inflated to normal pressure. The first annular surface 23, when the tire 30 is unmounted, forms an average angle beta with the axis of the tire, when the beads 33,53,63 are axially spaced a distance D equal to the design rim width. The average angle beta is at least three degrees greater than the angle formed between the mating bead seat 42 of the design rim 40 and the axis of the tire. The second surface 24 is designed to be in contact with an annular flange 44 portion of the design rim 40 when the tire is mounted and inflated to normal pressure. The second surface 24A is inclined relative to a plane P perpendicular to the axis of rotation, at an angle alpha at least three degrees less than the angle formed between the rim flange 44 and the plane P. Preferably the angle alpha is in the range of 3 DEG to 20 DEG ) more preferably 3 DEG to 15 DEG while the angle beta is in the range of 8 DEG to 25 DEG , more preferably 8 DEG to 20 DEG . The angular relationships relative to the design rim flange 44 permit the bead 33,53,63 and lower sidewall 21B of the tire 30 to rotate slightly upon mounting to the design rim 40, thereby improving the stiffness and handling characteristics of the tire 30.