--- title: Axle loads description: How Cargo Marshal checks the axle loads of a road Unit, which inputs it uses, and where the built-in values come from. --- A load can stay under the trailer's payload and still overload one axle. For road equipment that has an **axle profile**, Cargo Marshal works out the load on every axle (group) from the cargo's weight and where its centre of gravity sits along the deck, and warns when a limit is exceeded. > **Advisory, not a legal determination** > > Axle loads are an advisory for the finished arrangement. They never move cargo > or block a save, and they are not checked while the Unit is partly loaded. The > built-in values are typical figures — check your vehicle's plate and papers > before you rely on them. ## What is checked Only the length position matters: the cargo weight at its centre of gravity, plus the empty weights, is shared between the supports by lever arms (a beam on two supports). - **Semi-trailer.** The trailer rests on its kingpin and its axle group. The kingpin load goes onto the tractor's fifth wheel, which shares it between the steer and drive axle. - **Truck or van.** The deck rests on the front and rear axle. For each Unit you get: - the load on every axle (group) against its maximum, - the **steer axle share**: the steer (front) axle's part of the load on the vehicle that steers. Too little and steering and braking suffer; the default minimum is 20%, - with a tractor, the **drive axle share**: the drive axle's part of the gross combination weight. Too little and the combination lacks traction; the default minimum is 25%, as Directive 96/53/EC asks in international traffic, - the gross weight against its maximum, when one is set, - the **load distribution** diagram: the most cargo weight allowed for each centre-of-gravity position along the deck, with this load as a dot. Near the front wall the kingpin or front axle limits it, near the door the rear axles, the steer share or the drive share do. Over a limit, the Warnings list names the Unit and the axle, for example "Unit 1: drive axle load 12,400 kg of 11,500 kg allowed". Cargo concentrated far behind the trailer axle group can pull the kingpin (and the tractor's drive axle) upwards: the Warnings list then says that axle **would lift off**, and the load distribution diagram never allows such a load. The same numbers appear in the Loading Report. After a manual edit in the viewer they update straight away. ## Inputs Set the axle profile on a road Equipment Type in the Equipment Library (Axle loads). Positions are measured along the deck from the front wall; a negative value is ahead of it (a truck's front axle). | Semi-trailer | Truck or van | | ----------------------------------------------------------------------------------------------------------------------- | ----------------------------------- | | Kingpin position | Front axle position | | Axle group centre | Rear axle position (group centre) | | Trailer empty weight and where it acts | Empty weight on each axle | | Kingpin and axle group maximum | Front and rear axle maximum | | Tractor (optional): wheelbase, fifth wheel ahead of the drive axle, empty weight per axle, steer and drive axle maximum | Gross vehicle maximum (optional) | | With a tractor: gross combination maximum, minimum steer and drive axle share (all optional) | Minimum steer axle share (optional) | A Load Plan keeps a copy of the profile, like every other equipment value. Editing the library later does not change existing plans; reset the plan's equipment to take the new values, then Calculate again. ## Built-in values | Equipment | Typical values | | --------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | EU curtain, box, mega | Kingpin 1,300 mm behind the front wall, tri-axle group centre 9,430 mm (kingpin + 8,130 mm), trailer empty weight as the type's empty weight at 5,700 mm, kingpin 12 t, axle group 24 t; 4x2 tractor with 3,700 mm wheelbase, fifth wheel 700 mm ahead of the drive axle, steer axle 7.5 t, drive axle 11.5 t; 40 t gross; steer share at least 20%, drive share at least 25% | | US 53 ft | Kingpin 914 mm, tandem centre 13,300 mm; steer axle 12,000 lb, drive and trailer tandems 34,000 lb each, 80,000 lb gross | | Box truck (7.5 t) | Front axle 900 mm ahead of the box, rear axle 3,800 mm behind its front; axles 3.7 t and 5.6 t; 7.5 t gross | | Van (3.5 t) | Front axle 1,550 mm ahead of the load floor, rear axle 2,775 mm behind its front; empty weight 2.4 t (1.45 t front, 0.95 t rear); axles 1.8 t and 2.0 t; 3.5 t gross | Sources: - Directive 96/53/EC as implemented in the German StVZO §34: 11.5 t drive axle, 24 t tri-axle group with 1.3 m to 1.4 m spacing, 40 t combination. - Regulation (EU) 2021/535 Annex XIII: at least 20% of the load on the steered axle(s) as a design requirement. - Directive 96/53/EC Annex I 3.4: at least 25% of the total laden weight on the driving axle(s) in international traffic. - Schmitz Cargobull S.CS: 8,130 mm from the kingpin to the axle group. - US federal limits: 12,000 lb steer axle, 34,000 lb tandem, 80,000 lb gross. The kingpin position, tractor figures, and empty-weight centres are typical, not measured values. Duplicate a built-in type and enter your own vehicle's figures for a reliable check.