According to the present invention there is provided a wheel diagnosis system (DS) for diagnosing a wheel (12) under test mounted to a vehicle and including at least a rim (18) and a tire (13). The wheel diagnosis system comprises a plurality of sensing units (1, 2, 3) being adapted for scanning predetermined surfaces of the wheel under test when the wheel under test is rotated, a supporting unit (5) to which the plurality of sensing units is mounted. Specifically, the supporting unit is freely movable relative to the wheel under test, and the sensing units are located at different positions on the supporting unit for scanning different portions of the predetermined surfaces of the wheel under test and collecting data of the operation result when the supporting unit is placed at the wheel under test at a predetermined scanning position. The present invention further refers to a method of diagnosing the condition of the wheel under test mounted to a vehicle.