A trailer's steel specification is one of the biggest factors in its weight, durability, and price — yet it's rarely explained in plain terms. Here's what the most common grades actually do.
Structural Steel: ST-52 / S355JR
The main chassis and longitudinal beams of most heavy-duty trailers are built from ST-52 (equivalent to S355JR under EN 10025). This is a fine-grained structural steel with a yield strength of roughly 355 MPa, offering a solid balance between strength, weldability, and cost. It's the standard choice for load-bearing frames across the industry, including lowbed and tipper chassis.
Wear-Resistant Steel: Hardox 400 / 450 / 500
For tipper and scrap tipper bodies that take direct impact from loading — rock, scrap metal, aggregate — a structural-grade steel alone wears out too quickly. Wear-resistant steels such as Hardox 400, 450 or 500 (the number refers to Brinell hardness) are used instead. The higher the number, the harder and more abrasion-resistant the plate, at the cost of being slightly harder to form and weld. This is why body thickness and steel grade are usually specified together as an "optional" upgrade on tipper products — the right combination depends on what you're actually loading.
Why Not Use the Hardest Steel Everywhere?
Because weight matters as much as strength. A trailer built entirely from high-hardness plate would be heavier, more expensive, and would reduce the vehicle's net payload — the opposite of what a buyer usually wants. Good trailer engineering uses structural steel where rigidity is needed and wear-resistant steel only where direct abrasion occurs, keeping the empty weight as low as possible without sacrificing service life.
What to Ask Your Manufacturer
When comparing quotes, ask specifically which steel grade is used for the chassis, the floor, and the side/rear walls — and at what thickness. Two trailers can look identical in photos and have very different service lives underneath.
Foxon Trailer builds its chassis in ST-52 (S355JR) as standard, with Hardox 450/500 available as an option for tipper and scrap tipper bodies. To discuss the right specification for your cargo, fill out our quote request form.