According to the different stress conditions and structures of the car body, it is divided into load-bearing type and non-load-bearing type. There is no rigid frame in the car with a load-bearing body, and the front, side panels, rear and floor are strengthened. The engine, front and rear suspensions, part of the transmission system and other assembly components are assembled on the body, and the load of the body is transmitted to the wheels through the suspension device. Most cars use a load-bearing body, which is low-noise, light-weight, relatively fuel-efficient, but relatively low in strength. Cars with non-load-bearing bodies have a rigid frame, also called a chassis rail frame. The engine, transmission system, body and other assembly components are fixed on the frame, and the frame is connected to the wheels through front and rear suspension devices. It has the advantages of high chassis strength, good anti-bump performance, and the body is not easily deformed. Non-load-bearing bodies are large in size and weight, and are generally used in trucks, buses, and off-road vehicles. The following body carrying methods can include: loaded and unloaded bodies; the rear structure following the shape of the body can include: folding rear body, straight rear body, cockpit rear body and short rear body; follow The body-shaped box structure can include: three-chamber body, two-chamber body, and single-chamber body. There are three types of car frame structures: 1. For cars with non-load-bearing bodies, the frame is rigid, also called chassis girder frame. The connection between the frame and body is flexible through springs or rubber pads. The engine, part of the transmission system, body and other assembly components are fixed on the frame through suspension devices, and the frame is connected to the wheels through front and rear suspension devices. This non-load-bearing vehicle body is large in size, heavy in weight and high in height. It is generally used in trucks, buses and off-road jeeps, but there are also a small number of luxury cars because it has good stability and safety. 2. Cars with a load-bearing body do not have a rigid frame, but only strengthen the front, side panels, rear, floor and other parts. The engine, front and rear suspension, part of the transmission system and other assembly components are assembled on the body at the position required by the design, and the vehicle load is transferred to the wheels through the suspension device. In addition to its inherent load-bearing function, this load-bearing vehicle body must also directly bear various load forces. After decades of development and improvement, the safety and stability of the load-bearing body have been greatly improved. It has the advantages of small weight, low height, no suspension device, and easy assembly. Therefore, most cars use this body structure; 3. The body and frame are rigidly connected through threaded connections, riveting or welding. In this case, the car body not only bears the above-mentioned loads, but also helps to strengthen the frame to a certain extent and share part of the load of the frame.