The speed is slow and the sense of stagnation is strong when riding by human power. 

1. The friction between the front brake or the holding brake (brake expansion) and the rotating part: adjust the gap between the front and rear brakes and the rotating parts, not only to make the rotation flexible, but also to ensure good braking performance.

2. The chain is too tight: adjust the front and rear position of the rear axle;

3. The front and rear axle blocks and the middle axle parts and caps are too tight or the parts are worn: loosen the fasteners or replace or repair the worn parts;

4. The front and rear tires are insufficiently inflated: the tires are inflated to foot.