All weight from front to rear axle 4 (6, 8) wheel support, good stability, wide adaptability. The front wheel steering institutional sub-wheel steering and axle steering two types. The wheel steering style rut tractor trailer passing rut basically the same, the driver does not have to be looking back. Wheel in the frame on both sides of the lower carriage bearing surfaces, but a larger turning radius. Axle steering wheels of the trailer to the frame below rotary the carriage bearing surface, small turning radius of the unit, but the trailer rut tractor ruts inconsistent. 15 kilowatts or more universal wheeled tractor trailer in the use of pneumatic brake on a tractor equipped with a pump, brake linkage to the tractor brake pedal brake valve control. Brake valve adjustment so that the trailer brake slightly ahead of the tractor so that the tractor trailer impact, resulting swing affect the safety and operator comfort. The pneumatic braking inflation and breathe two types, respectively, in the state of inflation and breathe brake. Breathe brake system of the trailer and tractor accidentally disengaged self-braking, also known as a fail-safe braking system, but its structure is more complex.