An unbalance mass at the front side of a single wheel unit, an unbalance mass at the reverse side of the single wheel unit, a phase difference between the unbalance mass at the front side and the unbalance mass at the reverse side of the single wheel unit, a primary component amplitude of radial run-out of the single wheel unit, a phase angle of the primary component of the radial run-out of the single wheel unit, a contribution coefficient in which the radial run-out of the single wheel unit is transmitted to an RFV, an unbalance mass at the front side of a single tire unit, an unbalance mass at the reverse side of the single tire unit, a phase difference between the unbalance mass at the front side and the unbalance mass at the reverse side of the single tire unit, an RFV primary component amplitude of the single tire unit, and a phase angle of the RFV primary component of the single tire unit are measured and the measured values are input. Evaluation functions for evaluating an optimum assembling angle of the tire and the wheel in accordance with an object are determined, and the optimum assembling angle is determined and output as a predicted angle using the determined evaluation functions.

An apparatus for electromagnetically and rotationally vibrating a rotary body supported by bearings. The apparatus comprises a ring-shaped magnet bipolarly magnetized and mounted on a shaft of the rotary body coaxially, a ring-shaped stator having a coil and adapted to generate a rotating magnetic field by controlling an electric current supplied to the coil, and a frequency-variable vibration power source adapted to supply alternating electric power to the coil in the stator. The magnet and the stator have different magnetic radii and are disposed so as to be opposed to each other in a direction identical with the magnetization direction of the magnet. Thus the rotational exciting force is applied to the rotary body by an interaction of the rotating magnet field generated by the stator with the magnet. This electro-magnetic rotary vibrator can be applied to a damper for offsetting the unbalanced vibration of a rotary body.

In a method of correcting the unbalance of a rotating body (Fig. 5, R), data relating to initial unbalanced amounts or weights (U1, U6) at two predetermined correcting planes axially spaced and passing through the body is processed to determine correcting positions (2 to 5) and corrective machining weights (u2 to u5). The correcting positions and corrective machining weights are used for calculating the location of each center of gravity of each corrective machining portion and residual unbalanced amounts (U7, U8) in the axial direction on the assumption that corrective machining has been effected. The value of each of the residual unbalanced amounts will be compared with a predetermined value corresponding to its tolerance. If the value exceeds the tolerance, new initial unbalanced amounts or new correcting planes are assumed so that the new data will be converted into new initial information (U1', U6'; Fig. 11, U"(Zl'), U"(Z6')) to be fed back to the original step (16) of processing the initial unbalanced amounts. By repeating the operating processes (16 to 23) the residual unbalanced amounts will be within the tolerance so that accurate corrective machining can be effected, balancing the rotating body with a one-time machining.

In a method of correcting the unbalance of a rotating body (Fig. 5, R), data relating to initial unbalanced amounts or weights (U1, U6) at two predetermined correcting planes axially spaced and passing through the body is processed to determine correcting positions (2 to 5) and corrective machining weights (u2 to u5). The correcting positions and corrective machining weights are used for calculating the location of each center of gravity of each corrective machining portion and residual unbalanced amounts (U7, U8) in the axial direction on the assumption that corrective machining has been effected. The value of each of the residual unbalanced amounts will be compared with a predetermined value corresponding to its tolerance. If the value exceeds the tolerance, new initial unbalanced amounts or new correcting planes are assumed so that the new data will be converted into new initial information (U1', U6'; Fig. 11, U"(Zl'), U"(Z6')) to be fed back to the original step (16) of processing the initial unbalanced amounts. By repeating the operating processes (16 to 23) the residual unbalanced amounts will be within the tolerance so that accurate corrective machining can be effected, balancing the rotating body with a one-time machining.