Abstract: A method and apparatus for assembling a tire with a disc wheel under the optimum condition, in which inner diameter variation of the disc wheel, radial force variation of the tire proper, radial force variation of a wheel assembly body and existing assembled condition are displayed on separate channels of a display device, respectively. The radial force variation of the tire proper thus displayed is phase shifted by an angle at which the radial force variation of the wheel assembly body becomes minimum. The tire is then displaced with respect to the disc wheel by the above angle so as to obtain the optimum assembled condition.