The research I’ve done into vehicles over the past two years, the one thing I’ve never found is – you can never reach your legal GCM – and the answer is simple.
Nobody tells you this, and its something you have to research and factor within your specific setup. Lots of talk on GVM and GCM, ball weight being part of your GVM, but nobody is saying that you can not reach your legal GCM.
You have your vehicle GVM, GCM and your trailers ATM. If you have a 7000kg GCM, 3500kg GVM and 3500kg ATM, you’re over-weight, no longer legal nor insured. Check your insurance policy on that point, I guarantee you’re not insured if any part of your vehicle (vehicle or trailer) is overloaded.
Insurance demands legal weight. If your trailer is fully loaded to its ATM, then a minimum of 10% is your ball weight. You may actually find your ball weight is much higher due to how you’ve loaded your vehicle, ie. too much weight forward of the tow axle.
Your ball weight becomes part of your GVM, so 350kg ball weight average when fully loaded to 3.5T ATM, that means your GVM limit is actually 3150kg, fully loaded with you and passengers in the vehicle, as that 350kg has to be left available for transfer when connected.
It means you can only ever reach a maximum GCM that is less your ball weight. You can’t add that 350kg to your tow vehicle, as that would overload the ATM, back to uninsured.
So for every average 7 Tonne GCM, you’re really limited to a maximum GCM of 6650kg, as neither vehicle can be overloaded uniquely or when combined together.
Food for thought.