A tire profile (12) includes a tread (16), a shoulder (18), a flat portion (20), an upper sidewall (22) and a lower sidewall (24). The shoulder (18) is provided in contact with a tread (16) at a point (Pa). The flat portion (20) is provided in contact with the shoulder (18) at a point (Pb). The upper sidewall (22) is provided in contact with the flat portion (20) at a point (Pc). A system including an input portion and a calculating portion is used for designing the profile (12). When the numeric values of a radius of curvature (R1) of the shoulder (18) and an inclination angle (.theta.) of the flat portion (20) are input by the input portion, the calculating portion calculates a length (L) of the flat portion (20) and a radius of curvature (R2) of the upper sidewall (22). Based on the input numeric values and the calculated numeric values, the profile (12) is drawn by CAD software.