DEKRA experts warn against improper use

Do not overload trailer coupling

Jul 13, 2023 Automotive

A trailer coupling on a car is a fine thing. If there is something larger to transport around the house or garden, a trailer can be attached to the rear of the vehicle in no time at all. A bicycle carrier is also quickly mounted. However, DEKRA experts warn against putting too much strain on the trailer hitch. This can all too easily lead to damage to the coupling itself, but also to the towing vehicle as a whole.

  • Incorrect use can cause damage
  • Call in experts after rear-end collision
  • Check thoroughly before going on vacation
The connection between car and trailer has to withstand a lot. When accelerating, braking, driving uphill and downhill, strong forces are applied – due to the towed mass, vibrations, crosswinds and much more. To ensure that trailer couplings can withstand such stresses, they are subjected to extensive dynamic testing on a test rig before approval.
Observe maximum values for towing capacity and drawbar load
But what can drivers expect a trailer coupling to withstand? Important benchmarks are the permissible trailer load and the drawbar load with which a trailer acts on the coupling. Anyone driving a towed vehicle is responsible for ensuring that the maximum values stated in the registration documents for the vehicle and trailer coupling are adhered to. DEKRA experts also strongly advise that the instructions in the operating manual for the coupling be followed closely.
The experts warn against loading the trailer coupling more heavily than is approved in the documents. For example, if you use it to pull a tree stump out of the ground or drag logs, you can easily overload the hitch. Such misuse can lead to excessive wear or even permanent damage, for example cracks or deformation. With further use, there is then a risk of sudden failure.
The towing device also does not easily withstand a rear-end collision. In particular, a point impact with high force peaks can cause considerable damage to the coupling and suspension. This often makes it necessary to replace the trailer coupling. It is therefore advisable to have the damage assessed by an automotive workshop or a qualified automotive expert.
Check before the start of the vacation
Trailer couplings are in heavy use during the travel season, for example for towing a caravan or transporting bicycles on a rear carrier. To prevent breakdowns on the vacation trip, DEKRA experts recommend to thoroughly check the coupling before the start of the trip in accordance with the instructions in the owner's manual.
Particular attention should be paid to the following points:
• The trailer coupling must sit in the mount without play when mounted, even when shaken firmly. On certain models, it must be locked, and the key removed. On more modern variants, an unlocked state is indicated in the instrument cluster. If the ball bar is not properly locked, there is a risk of accident.
• The condition of the trailer socket and the electrical connection to the trailer or carrier are also part of the check. Are the lighting systems working? This is even more important if adapters or cable extensions are used.
• If a caravan is equipped with a stabilizing device, the instructions in the trailer's operating manual regarding the required clamping force must be observed.
• The check also includes an inspection of the friction linings of the stabilizer. They must not be dirty, contaminated with lubricant or worn. In most cases, wear marks on the friction linings are visible and indicate the state of wear.
• It is also important to check whether the breakaway cable is properly hooked into the eye provided for this purpose on the coupling of the towing vehicle. This ensures a certain residual safety in the event of a possible separation from the towing vehicle.