In recent years, with the continuous development of vehicle technology and the tourism industry, RV appears more and more commonly. In particular, the emergence of the C6 driver's license, the rise of the trailer type RV played a role in promoting. Rv refers to a special vehicle designed with tables and chairs, sleeping utensils, cooking utensils, storage, bathroom, lighting, air conditioning and additional facilities in the compartment. It is mainly used for tourism and field staff camping. It belongs to a movable model with necessary facilities at home. Top semi trailer manufacturers claimed In the past, the one-piece RV was more common, that is, the cockpit and the carriage were integrated. trailer type RV is different, its own more like a carriage, can not drive alone, need to use the front traction vehicles to achieve driving, such as pickup trucks, passenger cars, can be towed hanging RV carriage. In this way, when the car is not normally used, the owner can remove the car and the tractor, use the tractor alone, and connect it together when the car is needed, which can improve the efficiency of the vehicle to a certain extent. In fact, this RV is also called "hostel trailer", belongs to a special trailer model, with the ordinary vehicle driver's license not the same, to have A2 trailer class driver's license to traction such a carriage. But now the driver's license regulations have been updated. If the total mass of the tractor plus the carriage is less than (not including or equal to) 4500kg, you can apply for the C6 license, as long as you can get the C6 license. If you weigh more than 4500kg, you have to use a Class A2 license. At present, the design and specifications of numerous domestic light trailers can essentially meet the driving requirements of C6 driver's license. It is worth mentioning that at present, only A2 driver's license users can be directly compatible with C6, without the need to apply for a separate driver's license, and the rest of the driver's license types need to apply for the C6 driver's license type dedicated to light tractor-trailer. There are also different classifications for semi-trailers, with two main categories: semi-trailers and mid-axle trailers. While both types of vehicles are eligible for the C6 license, there are different requirements for the tractor class. Among them, the semi-trailer and transport semi-trailer principle is similar, is with gooseneck, need to be pulled through the saddle, need to be pulled by a light truck with a connecting plate, such as pickup trucks, can not use passenger cars as tractors. The middle axle caravan and the middle axle semi-trailer have the same principle. When evenly loaded, the center of mass of the trailer is close to the axle position, the traction device cannot move vertically relative to the trailer, and when connected with the tractor, there is only a slight vertical load acting on the tractor, which can be pulled by the passenger car. Owners can check their trailer license to see if the vehicle is registered properly. It is essential to note that, no matter what kind of model is used when the tractor, must have traction qualification. With the rise of the trailer, the trailer type of RV, the market demand for the axles and axle of the RV also began to rise gradually. Similar to the axle principle of the transport semi-trailer, the rear axle of the hostel trailer is also a support bridge, which does not have the steering or driving function. It mainly assumes the functions of loading, braking, maintaining running and reducing the vibration of the carriage. The difference is that the rear axle used by the RV is considerably smaller than the rear axle of the semi-trailer. At present, the tonnage of the semi-trailer bridge in the market is about 13t, and the tonnage of the main lightweight semi-trailer bridge is also about 10t. The rear axle tonnage of the RV is typically concentrated in the following 6t, such as 5t, 3t. In addition to smaller tonnage, RV rear axle parameters such as wheel pitch, currently there is no clear, unified standard reference, relatively niche, most need to be customized production according to the detailed needs of customers. To some extent, this puts forward higher requirements for the production experience, technology and process of manufacturers. Especially for those brands that do not have specialized factories and purchase semi-finished products from outside for assembly and sales, it is difficult to meet customers' customized requirements on parameters. From this point of view, in the purchase of RV axle, as much as possible to choose those with independent production capacity and quality assurance ability of the brand, not only according to the customer's model tailored to correctly match the axle, but also can avoid or reduce the subsequent use of numerous problems that may occur.