Schweriner CS

At a length of 12,625 mm and a width of 2,500 mm, the CS 40 G sits at the edge of the road dimensions allowed without a special permit. An unladen weight of 4,200 kg leaves a payload of 32,300 kg: almost eight kilograms of cargo for every kilogram of the vehicle's own weight, a ratio only a frame and axles designed for high axle loads can carry.

Category O4 requires air brakes, not the simple overrun brakes of light trailers. A trailer of this class is towed by vehicles holding driving licence category CE, in practice semi-tractors or heavy trucks with a matching towing capacity and coupling load.

Buying a used trailer this heavy, the frame comes first: cracks at welds and cross-members at this axle load result from material fatigue, not accidents. The air brake system needs checking for leaks and response time, the axle bearings for play, and the tyres must match the registered axle load, not just the rim size. A look at the service history for any repaired cracks in the frame is worthwhile too, given the loads this class of trailer carries on a daily basis.