When choosing the chain and sprocket of TVS ROCKZ125, you must pay attention to whether the two match and ensure the concentricity of the sprocket and the tire (sprocket seat). Otherwise, the chain will be tightened and loosened, causing early wear. When installing, place the sprocket on a non-worn sprocket seat, install the sprocket fixing screws, and put on locking washers. Do not tighten the screws too tightly. Install the chain together with the tires on the car, and then install the chain. After tightening the chain slightly, slowly turn the rear wheel and observe the tightness of the chain. If the chain is loose and tight, it means that the sprocket and tire (sprocket seat) are not concentric.