Tare weight, GVM, GTM, ATM, GCM whats it all mean?
Tare weight is the unladen mass of the vehicle as originally manufactured, that is all tanks empty, no accessories like gas bottles etc.
GVM/ATM – Gross Vehicle Mass/Aggregate Trailer Mass
GVM is Gross Vehicle Mass, this is the maximum weight of the vehicle when fully loaded. As applied to caravans or trailers the correct terms is ATM or Aggregate Trailer Mass which is the GTM (see below) plus the weight placed on the ball of the towing vehicle or ball weight.
When recorded for a trailer or caravan in the authorities system there is no facility for ATM so GVM is used.
GTM – Gross Trailer Mass
GTM or Gross Trailer Mass applies to caravans and trailers and is the maximum weight that can be transferred to the ground via the wheels.
GCM – Gross Combined Mass
GCM or Gross Combined Mass is the combined maximum weight of towing vehicle and trailer or caravan combined.
Now for some examples and maths!
Lets take a typical example we see every week, a 200 series Landcruiser and a Jayco caravan.
Car GVM 3350kgs towing capacity 3500kgs
When fully loaded to the manufacturers maximum this gives a GCM of 6850kgs
Our Jayco Silverline caravan has a GVM of 3300kgs, coupled with our vehicle gives
Car GVM 3350kgs + Van GVM 3300kgs = GCM 6650kgs
These limits are the maximum weights you can legally carry, without knowing you could be breaking the law or perhaps worst case not covered by insurance in the event of an accident.
Can we upgrade or increase these limits legally?
Yes is the short answer, how that can happen and by how much is variable depending on the vehicle construction, aftermarket replacement parts available and modifications that may have been done or need to be done.
The 4WD is rated at 3350kg GVM, most will be aware that after fitting a few accessories and throwing in a fridge and some drinks your car is now overweight. This is where some improved suspension and a compliance certificate can increase the GVM legally.
How with a new car? – Second stage compliance
Second stage compliance is where a aftermarket manufacturer like Lovells, Pedders, Old Man Emu, etc. have created a kit of components and applied for certification of those components to increase a vehicles GVM.
Second stage compliance can only be performed on a new vehicle before registration.
What about my used car? – VSCCS Compliance Certificate
After suitable components and modifications have been performed a Compliance Certificate (formerly called an engineers report) can be provided increasing the GVM, GCM, GVM or ATM.
How increasing about GCM or towing capacity?
GCM can be increased and we have performed some serious testing in this department, so we know what works!
Upgrading GVM on the car can reduce the GCM or Gross Combined Mass, this can be restored or increase on most vehicles with appropriate modifications.
Why is the GVM on my caravan so low?
Are you overweight? Well your van anyway 🙂
It is unclear why some manufacturers rate their caravans so low, however this problem is compounded by the accessories that may be fitted post manufacture, such as solar, extra batteries, additional water tanks, Air conditioning or a generator.
We have amassed a large database of caravans and modifications that may be done to safely increase GVM/GTM and in most cases a significant improvement in caravan stability when fully loaded.