Understanding vehicle masses

By: Tony and Denyse Allsop, Photography by: Tony and Denyse Allsop


All vehicles, whether towing or not, have a maximum legal load.

Understanding vehicle masses
How the load is distributed affects the axle loads and the tow ball mass, both of which also have restrictions for legal towing.

A while back, we wrote a blog on the relevant vehicle masses when towing, and we received some negative and disbelieving comments. While we would all like to believe that our vehicles will legally tow the advertised and promoted mass, there are still lots of caravanners who do believe this, and buy caravans accordingly. Frequently, we see rigs with vehicle and van (over)loaded to the max.

All vehicles, whether towing or not, have a maximum legal load. For the tow vehicle, this is the difference between the kerb mass (empty vehicle full of petrol) and the Gross Vehicle Mass (GVM), the maximum legal mass or weight of the fully loaded vehicle. When towing a trailer, the maximum legal mass of the two vehicles combined is the Gross Combination Mass (GCM). This is where problems can arise.

We haven't worried too much about our exact figures previously, as our van is only 1,800kg loaded, and we don't carry a fridge or other heavy items in the vehicle. To demonstrate the issues, I went looking for the GVM and the GCM for our Ford Territory.

Knowing these figures can be important for towing legally, but there was nothing in the manual, no plate in the engine compartment, and no figures on the sticker inside the driver's door. Also nothing by Googling the specifications nor on the Ford website.

A (long) call to our local Ford dealer had me referred to various departments and then a suggestion to look on the Redbook website! Unbelievably, a call to customer care at Ford initially drew a blank, but ultimately the figures were found in an old manual.

Our kerb mass is 2,047kg and the GVM is 2,590kg, which means that  we can carry 543kg (including ourselves) in our vehicle when we are not towing. The GCM is 4,750kg, so if the vehicle is fully loaded, we can legally tow 2160kg, not the advertised 2,300kg.

Alternatively, if we want to tow 2,300kg, we can carry only 403kg in the vehicle. Larger variations apply to some other vehicles, particularly those promoted to tow very heavy, large vans. Heavy bull bars and towing gear must be taken into account as part of your vehicle weight. If shown to be overloaded, your insurance and warranty could be void.

How the load is distributed affects the axle loads and the tow ball mass, both of which also have restrictions for legal towing.

You need your GVM and GCM as reference points when you take your rig to a weighbridge. We hope other caravanners find it easier to ascertain these. We'd like to hear about your experiences.

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