PURPOSE: To improve the tire uniformity, particularly the lateal force variation thereof by grinding a shoulder section properly with a grinder measuring a lateral force.

CONSTITUTION: An upper rim 3 and a lower rim 4 are arranged in the course of a conveyor 2 for carrying a tire to be inspected to rotate a tire 1 grasping it detechably. The upper rim 3 is connected to a motor 6 through a rotating shaft 5 while the lower rim 4 moves upward and downward freely with a cylinder 7. A rotary drum 8 presses against the tire 1 and is supported with a pair of upper and lower load cells 9. Grinding devices 11 and 12 for grinding upper and lower shoulders of the tire 1 has grinders 15 and 16 mounted at the tip of a rocking arm, rotating motors 17 and 18 for driving it and the like. The rocking arm is oscillated with servo cylinders 19 and 20 for controlling the position of the grinder. When a lateral force exceeds the reference grinding value, the corresponding one side shoulder is ground.