Towing Terms Explained: GVM, GTM, ATM and Towing Capacity
Towing terms can be confusing the first time you look at them.
You might be buying a caravan.
You might be checking if your ute can tow a boat.
Or you might be trying to understand what GTM weight meaning actually is.
You will hear terms like:
- GVM
- ATM
- GTM
- GCM
- Tow ball download
- Towing capacity
They all matter. And mixing them up can lead to overloading, instability and expensive damage.
This guide explains towing terms, including both Australian and US wording where relevant.
Quick Summary: Towing Terms Explained in 30 Seconds
If you only read one section, read this-
• GVM (or GVWR) is the maximum your vehicle can weigh when loaded.
• ATM (or Trailer GVWR) is the maximum your trailer can weigh when loaded.
• GTM is the weight sitting on the trailer wheels only.
• GCM (or GCWR) is the maximum combined weight of vehicle and trailer together.
• Tow Ball Download (Tongue Weight) is the downward force on the hitch.
• TARE is the empty weight (vehicle or trailer).
If you exceed any of these numbers, you are overloaded – even if the trailer looks fine.
Safe towing starts with knowing your numbers.
Vehicle Weight Terms Explained
These terms apply to your car, ute, SUV or truck.
What Is TARE Weight?
Tare (vehicle) means the weight of the vehicle as built at the factory.
It includes
• Standard equipment
• Engine fluids
• A small amount of fuel , often 10 litres under some standards
It does NOT include
• Passengers
• Cargo
• Accessories added later
In the US, the closest term is Curb Weight, which usually assumes a full tank of fuel.
What Is GVM?
GVM stands for Gross Vehicle Mass.
This is the maximum legal weight your vehicle can weigh when fully loaded.
It includes:
• The vehicle
• Full fuel
• Passengers
• Accessories
• Cargo
• Tow ball weight
In the US, this is called GVWR (Gross Vehicle Weight Rating).
If you exceed GVM, your vehicle is overloaded – even if you are under towing capacity.
What Is Towing Capacity?
Towing capacity is the maximum weight your vehicle is rated to tow.
But this number alone does not mean you are safe.
You must also check:
• GVM
• GCM
• Tow ball download
Many people focus only on towing capacity and forget the rest.
Trailer Weight Terms Explained
These apply to caravans, boat trailers, horse floats and work trailers.
What Is Trailer TARE?
Trailer tare is the empty weight of the trailer as it left the factory.
It does not includes:
• Tools
• Food/Gear
• Water tanks
• Gas bottles
In the US, this is known as Empty Weight.
What Is ATM?
ATM stands for Aggregate Trailer Mass.
This is the maximum legal weight of the trailer when fully loaded.
It includes:
• Trailer tare
• All cargo
• Water tanks
• Gas bottles
In the US, this is known as Trailer GVWR.
ATM is the heaviest your trailer is allowed to be.
What Is GTM?
GTM stands for Gross Trailer Mass.
This is the maximum weight carried by the trailer wheels when connected to the vehicle.
It does NOT include the tow ball download.
In the US, the closest term is GAWR (Gross Axle Weight Rating).
GTM is the weight sitting on the trailer wheels only.
What Is Tow Ball Download?
Tow Ball Download is the downward force the trailer puts on your hitch.
In the US, this is called Tongue Weight.
Too much can overload the rear axle.
Too little can cause sway.
Most trailers sit safely around 8 to 12 percent of total trailer weight.
Combined Weight Explained
What Is GCM?
GCM stands for Gross Combination Mass.
This is the maximum total weight of:
• Loaded vehicle
• Loaded trailer
• Combined together
In the US, this is called GCWR (Gross Combined Weight Rating).
Even if your vehicle and trailer are individually under their limits, you can still be overloaded if you exceed GCM.
Common Towing Mistakes
Many first time towers
• Confuse ATM and GTM
• Ignore tow ball download
• Focus only on towing capacity
• Forget passengers reduce payload
• Forget water tanks add weight
Overloading increases:
• Tyre heat
• Brake stress
• Bearing load
• Risk of failure
Weight and heat always work together.
Simple Example
That is how people accidentally overload.
Towing Terms Comparison Table
| Meaning | Common AU Term | Common US Term |
|---|---|---|
| Empty vehicle weight | TARE | Curb Weight |
| Max loaded vehicle weight | GVM | GVWR |
| Empty trailer weight | TARE (trailer) | Empty Weight |
| Max loaded trailer weight | ATM | Trailer GVWR |
| Max weight on trailer wheels | GTM | GAWR |
| Downward hitch force | Tow Ball Download | Tongue Weight |
| Max combined weight | GCM | GCWR |
Recommended products for towing safety
Wheel Mounted temperature sensors
- Real-time data direct to your dashboard
- Easy installation
- Suitable for all trailers