A transformation matrix used for finding actual loads acting on a tire can be reliably calibrated. Using the calibrated transformation matrix, the translation and moment loads exerted on the tire can be calculated with a high degree of accuracy in a multi-component force measuring spindle unit including two multi-component force measuring sensors on locations spaced-apart from each other along the axis direction of a spindle shaft. The calibration method includes a step of measuring loads exerted on the spindle shaft, a calculation step using a measured load vector including the loads obtained in the measurement step and the transformation matrix applied to the measured load vector, to find an actual load vector including actual loads on the tire. Before the calculation step, a calibration step determines the measured load vector under a plurality of linearly independent test conditions and calibrates the transformation matrix based on the determined measured load vector.
展开▼
