I quote: (…) 4. Prerequisite (for 100 registration): Mass ratio The maximum permissible mass of the trailer (zG Anh) must not exceed the following value: zG Anh = X x m Pull fz empty with m Pull fz empty = Empty mass Towing vehicle Depending on the technical equipment of the combination, the following values apply to X: Technical equipment of the trailer without hydraulic shock absorbers with brake and hydraulic shock absorbers Caravans Other trailers 0.3 0.8 and 1.0* 1.1 and 1.2* respectively (… For my vehicle combination the factor is 1.1, I only need a few kg to reach it. Question: can the support load in this calculation be added to the unladen mass of the towing vehicle?