It’s important to understand the weights that are involved with towing, and the impacts that they will have on the way your vehicle drives. Important measures here are ATM (Aggregate Trailer Mass), GTM (Gross Trailer Mass) and Ball Load.
Aggregate Trailer Mass refers to the total weight of a trailer and its load when it is not coupled to a vehicle.
Gross Trailer Mass is the same trailer and load, but is the weight when it is coupled to the vehicle. This number will less, because of the Ball Load. Through the coupling, weight of the trailer is transferred to the vehicle, effectively making the trailer lighter.
Ball load is a very important facet to know about your towing setup. If you have too little trailer load, your vehicle will handle erratically, and can be downright dangerous on the road. If there is too much weight, you risk overloading the chassis and axle of your tow vehicle.
Our big advice here is that the local weighbridge is your friend. Get your tow vehicle and trailer in full touring trim, and take it down to the weighbridge to accurately see what you are weighing. Firstly, weigh your tow vehicle and trailer separately, and then all together. Knowing that your GTM, GVM (Gross Vehicle Mass) and GCM (Gross Combination Mass) is within specification is imperative from a legal point of view, and is very important for peace of mind and trip planning.
HOW TO UNHITCH SAFELY
1: Chock the trailer wheels front and back, and keep bystanders at least 15 metres to the side.
2: Engage the trailer brake
3: Lower the jockey wheel,ensuring the wheel is positioned sideways to inhibit movement.
4: Wind the jockey wheel out, taking weight away from the towball and onto the jockey wheel
5: Undo electrical connections
6: Undo the safety chains
7: unhitch your vehicle from the trailer, and slowly drive away.