In order to safely tow a trailer with a passenger car, very specific load distributions and permissible weight specifications must be adhered to. In this article, we have summarised for you what must be observed with regard to towing and drawbar loads and how the permissible towing loads are calculated:
Loads and their definition: What are trailer load, drawbar load and co.
When calculating trailer loads, in addition to the permissible total weight of the trailer, the actual mass from the drawbar and axle load as well as the total towing weight also play a role. To give you an overview of the relevant calculation parameters, we have briefly explained the most important terms here:
Towing load
The trailer load is the weight that a vehicle with a trailer is actually allowed to tow. The maximum towable mass therefore describes the maximum load that may be towed by the towing vehicle.
Drawbar load
The drawbar load describes the weight with which the trailer drawbar presses on the ball head of the coupling of the towing vehicle. It is the maximum weight that may act on the trailer coupling from above. The load contributes to how safe the combination is on the road and how much weight you are allowed to load onto the trailer.
Total towing weight
The total towing weight is usually given as additional information in the vehicle documents and must be taken into account in addition to the registered trailer load. The entry is often lower than the value that results when the permissible total weight of the towing vehicle and its maximum towed load are added together. If the towing capacity is fully utilised, the towing vehicle may no longer be fully loaded.
Unladen weight
The unladen weight is the mass of the towing vehicle with a 90 % full tank and the weight of the driver. It does not include the load in the vehicle or other persons sitting in it.
Axle load
Axle load defines the weight on the axle of a trailer. This value can be determined from the actual total mass by subtracting the drawbar load and dividing by the number of axles.
Where are the towing capacity and drawbar load of a trailer?
You can read in the vehicle documents which towing capacity is permissible for your vehicle. The maximum towable mass of the vehicle is stated in the registration certificate part I (new vehicle registration document) under no. O.1/ O.2. The total weight is stated under No. F.1 and the maximum possible drawbar load is stated under No. 13.
If you have an older vehicle registration document, you will find the towable mass under No. 28 / No. 29 and the total weight under No. 15. The maximum drawbar load can usually be found on a small plate on the inside of the rear panel or on the tailgate. There is also a corresponding label on the trailer. If the specifications for the maximum drawbar load on the trailer and towing vehicle differ, the lower value counts.
What you should know about the drawbar load
How is the drawbar load calculated?
The legal regulation states that the drawbar load must be at least 4% of the actual trailer weight and at least 25 kg. The regulations apply to single-axle trailers as well as to two-axle trailers where the distance between the two axles is less than one metre. The calculation of the minimum drawbar load is:
Actual trailer weight x 0.04
The actual drawbar load can be determined with a drawbar load scale or a bathroom scale can be used for an approximate measurement.
What happens if the drawbar load is too high or too low?
As a general rule, it is recommended to always use the maximum permissible drawbar load. This reduces the risk of the vehicle combination swinging and thus lurching. The following applies: high drawbar load = high driving safety.
Too low a drawbar load means that the trailer has too little load on the trailer coupling, which impairs traction. But too high a drawbar load is not good either, because in this case the trailer puts too much load on the trailer coupling. Exceeding the payload can also significantly impair driving safety and is prohibited or punishable with a fine according to §44 paragraph 3 StVZO.
What you should know about towing capacity
What is the maximum towable mass for a passenger car?
The permissible trailer load of a vehicle is regulated in the Road Traffic Licensing Regulations (StVZO) and depends on the vehicle class, model, construction and trailer coupling. When specifying the permissible trailer load, a distinction is also made between braked and unbraked trailers. While many small cars are limited to unbraked trailer loads between 400 and 750 kg, the loads for braked trailers are usually between 1 and a maximum of 3.5 tonnes. You can find out which driving licence class you need for which weight class here.
It should be noted that the actual trailer load achieved may not be greater than the permissible total weight of the towing vehicle (1:1 principle). In addition, the trailer must not be towed by the towing vehicle if the unladen weight of the trailer exceeds the maximum towed load, as this would mean that safety is no longer guaranteed.
You can find out how high the permissible trailer load is for your vehicle from the ADAC vehicle list.
What am I allowed to attach to my towing vehicle? A practical example to illustrate the point
For a box trailer K 2630-14-1550 (braked, total weight 2,600 kg, payload 2,250 kg) it turns out that the maximum load weight is 850 kg.
1,200 kg (maximum trailer weight of the towing vehicle)
- 350 kg (unladen weight of the trailer)
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= 850 kg (maximum weight of the load)
You can hitch this trailer to your towing vehicle without any problems. However, since the towing capacity of the towing vehicle is limited to 1,200 kg, the trailer may only be loaded with 850 kg, although it could carry loads of up to 2,250 kg.
Penalties and fines for a trailer load that is too high
Exceeding the load is considered a violation of the StVZO and will result in penalties and fines. This applies to an excessively high total weight, an excess of the towed and towing load as well as an excessively high axle and drawbar load. The amount of the fine depends on the percentage of the load that is exceeded. In Germany, the fine is between €30 and €425. Exceeding the limit by more than 5 % will also result in a point in Flensburg.
Conclusion: When you are on the road with your trailer, you should pay attention to both the trailer load and the drawbar load. On the one hand, this prevents overloading your trailer, on the other hand, it is also important for safety reasons to adhere to the prescribed values. Because only when the loads are optimally distributed does the trailer retain its driving safety. Also find out about the trailer loads applicable abroad, as these may differ from those in Germany.