1 The center shaft is damaged, or the clearance is large and loose, caused by the wheel disk wobble, caused by dropping the chain.

2 The wheel disk is bent. It needs to be corrected or replaced.

3 The rear wheel is not in the center of the rear fork, loosen the rear axle screw and adjust the wheel to the center.

4 Chain is too loose, chain free hanging 1-2 centimeters appropriate, too loose easy to drop the chain too tight to affect the inertia of the flywheel, the chain wear is serious, the riding resistance is also big. You can loosen the rear wheel screws and tighten the zipper to adjust the chain. If necessary, the chain will be intercepted two sections.

5 Chain wear is serious and has been scrapped, you can see the chain gap is too large. Need to replace the chain with a new one.