Technical knowledge: towing vehicle, trailer, coupling, brakes and lighting
Coupling and brakes
- Light trailers use a 50 mm ball coupling. The coupling head must latch with a visible or audible lock and be secured with its safety pin.
- The breakaway cable (prekidno uže) must be looped around a fixed point on the car, never around the ball itself, so that it applies the trailer brake if the coupling separates.
- Overrun brakes (inercijska kočnica) work when the trailer pushes the car; leave enough slack in the cable for full-lock corners.
- Raise and lock the jockey wheel before moving off; check the trailer chassis, mudguards and lights are secure.
Lighting
- A 7-pin or 13-pin plug feeds indicators, tail, brake, fog, reversing and plate lamps. Test every function with a second person - you cannot see brake lights from the driver's seat.
- A trailer needs its own rear registration plate and, where required, a second plate on the car's rear.
Tyres and load capacity
- Tyre load rating must cover the axle load; check pressures cold and look for cracks and age.
Worked example
A single-axle trailer with 1,300 kg MAM and a car coupling rated at 75 kg. Correct nose weight is 5–7% of the trailer's actual mass: for 1,200 kg that is 60–84 kg, so the car's 75 kg cap decides. A 90 kg generator loaded at the front panel overloads the coupling; move it 30 cm behind the axle and re-measure.
Traps that cost marks
Clipping the breakaway cable to the ball; testing lights alone; using a worn or greased ball that lets the head clatter; forgetting the safety pin; ignoring the coupling's vertical-load limit.