On the move with a boat & trailer – width, weights and loads


Width of the trailer – Up to a width of 2.55 m, transport is problem-free on most roads. Since the boat is usually wider than the trailer, you should pay particular attention to this dimension when buying a boat. From 2.55 m to 3 m, special permits for extra widths are relatively easy to obtain. From 3 m it gets complicated.

Weights and loads on the boat trailer

Particular attention is paid to the weights and loads. The variety of terms is confusing. In the case of the towing vehicle, we are talking about the gross vehicle weight, the trailer load and the vertical load. In the case of a boat trailer, it depends on the axle load, the gross vehicle weight and, in turn, on the vertical load. Let’s bring some light into the darkness.

The permissible total weight of the boat trailer is added up from the empty weight (dead weight) of the trailer and the payload. With all weight measurements, the empty weight (dead weight) of the trailer must of course be taken into account. This is stated in the manufacturer’s brochure. Whether it also includes possible additional equipment such as a support wheel, winch stand, slip rollers, tilting frame or slip trolley must be clarified before purchasing. This quickly adds up to a few additional kilos, which can reduce the available payload.

Since the trailer is supposed to carry a boat, the payload represents the boat weight. When buying a trailer, however, not only the boat weight but rather the boat weight when loaded should be taken as a basis. Including motor (s), batteries, tank contents and equipment such as anchors, lines, bathing ladder, tool kit and other possible equipment. Taken together, the weight of the boat and equipment must not exceed the specified payload of the trailer. Exceeding the permissible total weight has serious consequences. In this case, the general operating license not only expires for the boat trailer but also for the entire trailer and thus also the insurance cover in the event of damage.

The vertical load is the vertical force with which the weight of the trailer acts on the towing device (also called the coupling) of the towing vehicle. The maximum permissible vertical load is stated in the trailer’s operating license. How great the force is that acts on the coupling of the towing vehicle depends primarily on the center of gravity of the load.

Often, a few centimeters of the boat algae on the trailer forwards or backwards (if the design of the trailer allows this) is enough to influence the vertical load. In a simplified way, the vertical load can be determined with a bathroom scale and a block of wood, the height of which corresponds to the height of the coupling on the car or truck. In the case of trailers with a support wheel, this replaces the wooden block mentioned during weighing. The support wheel is then lowered so far that it corresponds to the height of the coupling of the towing vehicle.

However, it can only be done exactly with a calibrated vehicle scale and attached to the towing vehicle. This is where the axle load comes into play. To determine the axle load, only the trailer’s wheels are on the scales. Then the entire team (car + trailer) and the towing vehicle are weighed separately. If the axle load of the trailer, the total weight of the combination and the weight of the car are known, the vertical load can easily be calculated. It makes sense to use the permissible vertical load as much as possible. This ensures good driving behavior of the team. Nevertheless, the permissible support and axle load should not be exceeded!

Calculation example vertical load:

Carriage weight: 1,800 kg

– Car weight: 1,000 kg

-Trailer axle load: 750 kg
= Vertical load: 50 kg

Weights and loads of the towing vehicle

This brings us to another, important point: the maximum trailer load of the towing vehicle. The basic rule is: an unbraked trailer may weigh a maximum of half the permissible total weight of the towing vehicle, but not more than 750 kg. A braked trailer behind a car does not exceed the gross vehicle weight of the towing vehicle. Exceptions apply to vehicles which, according to the official definition, are off-road vehicles. These may pull a maximum of 1.5 times their permissible total weight.
In total, however, the actual trailer load (axle load + vertical load) for passenger vehicles, including all-terrain vehicles used as passenger cars, must not exceed 3,500 kg. How much a vehicle can pull depends on various factors. A rear-wheel drive vehicle can pull more than one with front-wheel drive. With all-wheel drive, higher trailer loads are possible than without. How much exactly a vehicle can pull is stated in the vehicle registration document. And this information takes precedence over the basic regulations.

If higher trailer loads are to be towed, only a truck can be used as a trailer tractor. For them, however, German autobahns are taboo on Sundays and public holidays and also on Saturdays during the summer vacation period. This also applies to off-road vehicles, which you are happy to allow at a cheaper truck tariff. Trailers at the weekend are therefore only possible with a car.

Permissible total weight and vertical load also play a role in the towing vehicle. Very important: the support load of the trailer must not exceed that of the towing vehicle. For example, if the trailer ABE allows 80 kg support load, but the car support load is limited to 50 kg, the lower value must be observed. Of course, the reverse is also true.
Of course, the permissible total weight of the towing vehicle must not be exceeded. That happens more often than you think. Four people and luggage for the 3-week vacation weigh a lot. In addition, there is often equipment from the boat (after all, the permissible total weight of the trailer should not be exceeded) and – the vertical load. This is added to the weight of the towing vehicle.

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