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Loads: regarding light trailers and the car’s weight

Correct loading

Ratchet strap

Ratchet strap.

The following are the basis for correct loading:

  • Secure the load with a strap or similar. Unsecured loads that slide around can cause major damage in the event of forceful braking or a collision.
  • Position the load right at the front of the boot so that it will not be projected forwards. If the load is already tucked right in against the back seats in the boot, it has nowhere to go in the event of forceful braking.
  • Position the heaviest part of the load at the bottom in order to reduce the risk of it being dislodged and potentially causing damage.

It is normally during braking that the load and fastenings are subjected to the greatest pressures. This means that the fastening must at least withstand a movement of:

  • 80% of the cargo weight in a forward direction.
  • 50% of the cargo weight in a backwards direction and to the sides.

If you have loaded a refrigerator weighing 40 kg onto a trailer, the straps must withstand a minimum pressure of 32 kg (80% of 40) in a forward direction and 20 kg (50% of 40) in the other directions.

Weight terminology

  • Unladen weight: Unladen car with standard setup including driver (75 kg).
  • Maximum load: Maximum permitted load in accordance with the registration certificate.
  • Total weight: Unladen weight + maximum load.
  • Gross weight: The weight at a given time.

Light trailer

With a category B licence, you are only allowed to tow a light trailer. Note that there is a difference between what is classed as a light trailer and whether or not the car is permitted to tow the trailer.

What counts as a light trailer?

  1. Trailer with a maximum total weight of 750 kg.
  2. Trailer where the maximum total weight for car + trailer is 3,500 kg (3.5 tonnes).

If point 1 (max. 750 kg) is met, point 2 does not apply.

Trailer, example 1
Car Trailer
Total weight: 2,100 kg Total weight: 1,400 kg
The combined total weight (2,100 kg + 1,400 kg = 3,500 kg) is 3.5 tonnes exactly, but does not exceed 3.5 tonnes.

This means that the trailer is classed as light.

Trailer, example 2
Car Trailer
Total weight: 1,800 kg Total weight: 2,000 kg
The combined total weight (1,800 kg + 2,000 kg = 3,800 kg) exceeds 3.5 tonnes, which means that the trailer is not classed as light.

Trailer, example 3
Trailer No calculations need to be done. The trailer’s total weight is less than 750 kg and is therefore always classed as light.
Total weight: 600 kg

Clarification about example 3

The trailer in example 3 is always classed as light, as it weighs less than 750 kg.

Does this mean that I can pull this trailer with any car?
– No, you must always check your car’s maximum trailer weight. A trailer can be classed as light but still be forbidden for you to pull, if the car cannot handle the weight.

My car weighs 3,500 kg and is designed to handle a 750 kg trailer. I have a regular category B licence. May I pull a 750 kg trailer and thus reach a combined total weight of 4,250 kg?
– Yes. The rule gives you the right to pull a 750 kg trailer. It is unusual for a car to weigh 3,500 kg, but if your car is that heavy, 3,500 kg + 750 kg is permitted on a regular category B licence (not extended B96, not BE).

Please note that this becomes invalid when the trailer exceeds 750 kg. Examples:

  • Car 3,500 kg + trailer 750 kg = 4,250 kg = allowed on a B licence
  • Car 3,499 kg + trailer 751 kg = 4,250 kg = not allowed on a B licence
  • Car 3,000 kg + trailer 800 kg = 3,800 kg = not allowed on a B licence

Is the car permitted to tow the trailer?

In practice, calculations are seldom necessary. All of the information you need is found in the car registration certificate:

Swedish car registration certificate.

The car with this registration certificate is permitted to tow a trailer weighing a maximum 2,100 kg, though not with a regular category B driving licence, as O.3 stipulates that the maximum trailer weight for a category B driving licence is 910 kg.

Am I permitted to use this car to tow a trailer weighing 2,300 kg with the extended B category (B96) or BE licence?
– No, as the maximum weight of 2,100 kg may never be exceeded, regardless of category. The car is not built to handle heavier trailers.

Ball pressure

Ball pressure is the pressure that the trailer’s coupling device exerts on the car’s towbar. Normally, the ball pressure should lie somewhere in the interval 30–100 kg.

High ball pressure

Excessive load at the front of the trailer. This results in poor traction with the front wheels, and may cause other road users to be dazzled by the dipped headlights.

High ball pressure
The load is at the very front of the trailer, and is therefore pressing the coupling device towards the ground. The car is forced to follow it, and as the car is straight, the front end is elevated.

Low ball pressure

Excessive load at the back of the trailer. This results in poor traction with the rear wheels. Can lead to a driving ban.

Low ball pressure
The load is at the very back of the trailer, and is therefore tipping the trailer backwards, which in turn pushes the coupling device upwards. The rear of the car is lifted by the coupling device.

Regulations concerning trailer brakes

  • A service brake must be fitted on trailers with a total weight exceeding 750 kg.
  • A parking brake must be fitted on trailers with an unladen weight exceeding 400 kg.

Marking heavy lorries and heavy trailers

Reflector on a heavy lorry:

Reflector on a heavy lorry

Reflector on a trailer with a total weight exceeding 3.5 tonnes:

Reflector on a trailer with a total weight exceeding 3.5 tonnes


The lorry has a trailer, which means that the overtaking distance will be longer.

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