PURPOSE: To permit the automatic adjustment of a distance between rims by a method wherein the holding mechanism of another bead section is operated to move the chucking rim to the most suitable position through the tire in accompanied with the setting of the position of the chucking rim for the holding mechanism of one bead section.

CONSTITUTION: A pair of bead section holding mechanisms H, K, holding rotatably the respective bead sections of the tire T, are provided opposingly on respective frames Fa, Fb arranged with a distance. The inner volume of a tire width regulating cylinder K1 and the total inner volume of a chucking rim operating cylinder K2 are made so as to be the same. When the moving amount of one rim H4 among respective chucking rims H4, K4 is determined, the moving amount of the other rim K4 is determined automatically without missing the revolving center L of the tire T and the distance between the beads of the rim may be changed automatically.