What a lot of people don’t realise is that there is also a plated weight for the front and rear axles.
This means that although you could be running legally overall, you could be illegal thanks to the weight being balanced too far to the front or rear.
A good truck will be designed so that if a weight is placed evenly across its body space, the weight will be distributed over the front and rear axles, but most pallets and parcels don’t come flat and as such, weight can be spread unevenly.
This is known as the see-saw effect, a rather appropriate description.
Additionally, if there is extra weight behind the rear axle, such as when a trailer is carried, the weight on the rear axle will increase but the front axle load will diminish.
If however the trailer is not loaded correctly and there is negative weight on the tow ball behind the rear axle, the weight on the rear axle will drop and the front will increase – this would be a highly dangerous situation as the whole vehicle would become unstable due to lack of trailer control.