PNEUMATIC TIRE DESIGNING METHOD

When a single performance or a plurality of antinomical performances are to be obtained, the best mode of a tire is designed under a given condition. A basic shape model using one block as a reference shape is obtained (100). An object function representing a tire performance evaluation physical amount, a constraint condition for restricting the tire shape, and a design variable which is an angle of a wall surface which determines the block shape are determined (102). Next, the design variable is varied continuously by .DELTA.r.sub.i to determine a modified shape model (104 to 108). A value of the object function of the modified shape model and a value of the constraint condition are calculated, and a sensitivity of the object function and a sensitivity of the constraint condition are determined (110, 112). A variation amount of the design variable which minimizes a standard deviation of block rigidities is estimated, a modified shape model is determined, an object function value is calculated, and a block shape forming the tire is determined by using the value of the design variable (114 to 120).