Composition and Classification of Semi-Trailer Suspension Systems

A semi-trailer suspension system consists of elastic elements, guiding devices, shock absorbers, buffer blocks, and lateral stabilizers. Generally, trailer suspension systems are divided into two types: non-independent suspension and independent suspension. Currently, the suspension systems of heavy-duty trailers in China are mainly non-independent suspensions, and the suspension elastic elements are generally leaf springs.

Types of Heavy-Duty Trailer Suspension Systems in China：

Leaf Spring Suspension

Leaf Spring Suspension, (or simply leaf spring suspension) also known as laminated spring suspension, is a historically significant and widely used automotive suspension system. Its core component is a single or a set of laminated steel plates made of spring steel, which absorb road impacts and ensure a smooth ride by flexing and deforming.This type of suspension is not widely used at present, and is mainly used on low-axle flatbed semi-trailers that transport goods at low speeds.

Single-point suspension

A single-point suspension reduces the common leaf spring suspension's front and rear supports to a single support connected to the vehicle body. Its load-bearing capacity is distributed across both the front and rear axles, resulting in a higher load-bearing capacity compared to a standard leaf spring suspension.

This type of suspension is less commonly used on ordinary semi-trailers and is primarily found on heavy-duty vehicles.

Leaf spring suspension

Leaf spring suspension, also known as tandem leaf spring balance suspension, is the common type of suspension using leaf springs. It mainly consists of leaf springs, suspension mounts (commonly called hangers), connecting rods, U-bolts, etc. The longitudinal forces on the vehicle body are directly distributed across a single axle.

The biggest advantages of this type of suspension are its low cost, high reliability, and ease of maintenance. Currently, over 80% of ordinary semi-trailers in China use leaf spring balance suspension.

Air Suspension

The most obvious feature of air suspension is its air spring system. Air springs are relatively lightweight, and the air inside the air chamber experiences minimal friction, resulting in almost no noise during operation. Furthermore, their lifespan is 2-3 times that of leaf springs. However, using air springs requires a system of rods capable of transmitting various forces and torques other than vertical forces, thus complicating the suspension structure. Additionally, air springs have stringent sealing requirements, leading to higher costs.

Currently, air suspension on trailers in China is primarily used in high-end applications such as precision instrument transport, tobacco transport, and hazardous chemical transport.