Guides
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.
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).
For each Unit you get:
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.
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.
| 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:
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.