The automotive tire being measured is loaded in advance by the load applying means, and the drum is driven to rotate the tire. A displacement of the rotatable shaft produced in response to a variation in the radial force acting between the tire and the drum is detected as a displacement of the movable member which is in turn indicated as the radial force variation generated on the tire. Thus, the apparatus can measure a radial force variation with precision under a condition approximating an actual running condition of automobiles.
