The towing number in a car advert is not enough to decide whether a loaded trailer is legal. A safe calculation uses the car’s approved braked or unbraked towing limit, the trailer’s maximum authorised mass (MAM), the loaded trailer weight, nose weight and the driver’s licence category. The lowest applicable limit is the one that governs the journey.
Start with the manufacturer’s handbook or vehicle plate. Confirm the maximum trailer weight for the exact engine and body style; a different version of the same model can have a different rating. Then check the trailer plate and work out what it weighs loaded. The trailer must not exceed its MAM, and its actual loaded mass must stay within the car’s towing rating. Check nose-weight limits for both the car and towbar as well.
Example: if the car is rated to tow 1,500kg braked but the trailer’s MAM is 1,800kg, the car’s lower 1,500kg rating still limits the trailer’s actual loaded weight. Loading it only to 1,400kg does not erase the separate licence test based on the permitted MAM of the combination. A Category B licence has specific trailer and combined-MAM conditions; category BE may be required for heavier combinations.
Do not calculate from the car’s kerb weight or rely on a sales description such as “tow-ready”. Extra passengers, luggage and accessories affect the car’s available payload and axle limits. A towbar’s rating may also be lower than the car’s. Ask the installer for the towbar’s plate and fitting details.
Once the figures agree, check that the trailer is balanced, the nose load is within limits and the load is restrained. For the licence calculation, see Car and Trailer Licence Ireland: B vs BE.
