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A leaf spring is a flexible structure used to support weight and absorb shocks. It has been used in trucks and trailers for decades; its design is simple but highly reliable.
The term “leaf” refers to the steel plates themselves; when stacked together, they resemble leaves, hence the name.
surface
A complete set of leaf springs actually appears quite simple—just a few curved steel plates stacked together.
The top section is the longest and is typically referred to as the main plate. Its ends are rounded and fitted with bushings, then connected to the frame via a leaf spring shackle or a mounting bracket. At the center, a leaf spring center bolt secures all steel plates together, while leaf spring clamps are usually added on both sides to prevent lateral displacement of the plates under load.
As for the material, most are made of specialized leaf spring steel, commonly silicon-manganese steel. This steel is characterized by a balance of strength and toughness. It can bear the entire vehicle’s weight while withstanding repeated bending without cracking easily.
When these components are assembled together, they form what we commonly refer to as a leaf spring.
principle
Understanding how it works is actually very simple.
When the vehicle comes to a stop, its weight presses against the springs, causing the steel plates to bend naturally.
When the wheel encounters a pothole, the spring compresses; after the impact, it rebounds, releasing the stored energy.
So why use a stack of steel instead of a single piece?
A single thick iron plate is too brittle and breaks after just a few repeated compressions. When the plate is divided into multiple layers, the blades rub against each other during operation. This friction absorbs part of the vibration and provides inherent damping effects, functioning like half a shock absorber.
Due to its multi-plate structure, only a few plates bear the load under light loads, while more steel plates share the pressure under heavy loads. This characteristic makes the leaf spring suspension system particularly suitable for freight vehicles.
This is the core principle behind how leaf springs work.
act on
Modern family cars generally no longer use leaf spring suspensions, yet these components remain indispensable for tasks requiring heavy-duty or strenuous performance.
Notably, in many leaf-spring suspension systems, the rear axle position is actually controlled by the spring itself—meaning the spring not only bears the load but also partially restricts the axle displacement.
Precisely because these components serve more than just elastic functions, any loosening of leaf springs, wear of bushings, or metal fatigue not only compromises ride comfort but also jeopardizes vehicle stability—especially evident in demanding applications like long-haul freight transport.
leaf spring vs coil spring
Coil springs are what you’ll usually find under passenger cars.
Leaf springs are built with load in mind. They can handle heavier weight and, in many setups, help keep the axle in position without adding extra linkage. That’s why you still see them on trucks and trailers.
They’re designed for different jobs. Comfort leans one way; durability and load capacity lean the other.
Overall, leaf springs feature a simple structure and reliable performance.
Hanging technology continues to advance, yet leaf springs remain dominant in specific applications—sometimes, simplicity is the advantage.
For many years, we have been committed to providing high-quality, high-performance automotive suspension products. If you have any questions about suspension systems, please feel free to contact us at any time.