1. Different properties: The hub is the rotating part of the wheel core connected by a column of inner contour steel of the tire. Brake drum is the friction coupling of drum brake, except it should have the strength and rigidity required as a component. 2, the device is different: The automobile brake except each kind of slow speed device, almost is uses the fixed element and the rotating element working surface friction to produce the brake torque the friction brake. The rims are fitted to the tire assembly to support the wheel portion of the tire. 3. Different composition: Hub Width is also known as the J value, the width of the wheel directly affects the choice of tire, the same size of the tire, j value is different, the choice of tire flat ratio and width is also different. Brake drums are cast in one piece from high strength gray iron or alloy iron containing CR. 1. When the wheel is hot, let it cool down naturally and then clean it. Don't use cold water to clean it. Otherwise, it will damage the wheel and even deform the brake disc and affect the braking effect. In addition, when cleaning aluminum alloy wheel with detergent at high temperature, the surface of the wheel will react, lose luster, affect the appearance. 2. When there is hard-to-remove tar on the wheel hub, try to remove it with a brush if the usual detergent doesn't work, but don't use a strong brush, especially an iron one, to avoid damage to the surface. 3. If you find a deep cut on the wheel hub, be sure to observe whether the metal surface is exposed. If you can't see the metal surface, it won't rust. Apply it bit by bit with the NIB and let the paint dry completely. If the metal is exposed, it's easy to replace.