Tire uniformity tester and tire uniformity measurement method

A tire uniformity testing machine, comprising:

• a spindle shaft that is able to forward rotate and backward rotate together with a tire while holding the tire;
• a spindle shaft drive device that forward rotates and backward rotates the spindle shaft and the tire held thereby;
• a drum that has an outer peripheral surface contacts a tread surface of the tire during testing;
• a pressing mechanism that supports the drum so as to rotate about a center axis of the outer peripheral surface, and moves the spindle shaft and the drum relatively to each other so as to be able to press the tread surface of the tire mounted on the spindle shaft against the outer peripheral surface of the drum;
• a uniformity measurement unit that measures uniformity of the tire during the forward rotation and the backward rotation based on a force generated on the drum while the tire is forward rotating and backward rotating;
• and
• a control unit that operates the spindle shaft drive device and the pressing mechanism in conjunction with the uniformity measurement unit so as to respectively control a rotational direction and a rotational speed of the spindle shaft and a relative position between the spindle shaft and the drum,
• wherein the control unit controls rotational drive of the spindle shaft and the relative position between the spindle shaft and the drum such that when the rotational direction of the spindle shaft is inverted between the direction of the forward rotation and the direction of the backward rotation, the spindle shaft and the drum are relatively moved so as to separate from each other, thereby causing the rotational speed of the spindle shaft to be 0 in a state where the outer peripheral surface of the drum and the tread surface of the tire are not in contact with each other.