Hello. First, the brake pad is worn to the limit, causing the brake pad to rattle with the brake drum or brake disc. Second, the bearing is short of oil and the oil seal is aging, which leads to abnormal sound of the bearing. Third, the steel ring is deformed or the fender is abraded. Fourth, the brake disc or drum splashes mud or grinds stones. These are the reasons that cause the rear wheel to rattle. I hope I can help you.