The support load is the force that acts from the drawbar onto the trailer hitch. The support load for single-axle trailers prescribed by law is 4% of the actual trailer weight. More than 25 kilogrammes are usually not necessary.
The support load of tandem trailers / trailers with a permissible total weight of more than 3.5 tons also require a support load of 4%, however it should not be higher than 500 kilogrammes.
Universal formula of the minimal support load:
minimal support load = actual trailer weight x 0.04
Effects on the driving stability
A higher support load means higher driving stability!
This is why it is sometimes necessary to put a burden at the front of the empty trailer to minimise the danger of lurching. As the support load acts on the trailer hitch, it is added to the weight of the towing vehicle. Therefore the trailer can be loaded heavier.
It there is too much weight on the trailer hitch, the front axle is strongly disburdened. This leads to bad steering and braking behaviour. If the support load is too low, the rear axle is disburdened too strongly, which leads to a higher risk of skidding. The maximum support load is given in box 13 of all vehicle registrations since October 2005. Earlier, information on the maximum support load were engraved directly on the trailer hitch or given on a sign at the back of the vehicle.