1. collision: the center of mass displacement caused by the deformation caused by wheel collision leads to uneven lining.
2. Difficulties in overlapping: Due to the positioning error of the hub and rim, it is difficult for the installation center and the rotation center to overlap.
3. Damage to the center of gravity: disassembly and assembly in the maintenance process destroyed the original integrated center of gravity, and the uneven thickness of COVID-19 caused by low positioning accuracy during tire retreading changed the center of gravity, thus becoming shiny.
4. Uneven density: Due to the uneven geometric density, there are inherent deviations in the centers of gravity of tires, rims and retaining rings.