AT A GLANCE

GCM is short for gross combination mass, which is the weight of the fully loaded vehicle and trailer.

GVM is gross vehicles mass, which is the weight of the car, any accessories, people and luggage. It also includes the weight of the trailer pushing down on the towball.

ATM is aggregate trailer mass, which is the weight of the fully loaded trailer.

Towball down-weight (or down-load) is how much weight is pushing down on the towball. Typically it should be 10 per cent of the weight of the trailer. Payload is how much weight you can put in the car, including people and luggage.