Distinguishing Features of Transport Side wall Semi-Trailer    1. Steel structure: Steel frames are built with top-class hot rolled or rolled steel plate, automatic welded longitudinal beam and adopting advanced sanding and painting process as preliminary treatment. 2. Different types of suspension are designed for various operating condition: Bogie suspension; Air suspension; Mechanical suspension. 3. Automatic tire inflation and pressure sensor system is optionally available for enhanced safety and better fuel economy.