Don't ask the forum, you will only get wrong answers!
The NSW rules can be seen at
Towing Trailers
I am sure that Vicroads will have something similar.
The most important bits are...
Quote:
TOWING RATIO REQUIREMENT
The loaded mass of the trailer must not exceed the lesser of:
Rated capacity of the towbar and tow coupling.
Maximum towing capacity of the vehicle.
Maximum carrying capacity of the trailer.
Maximum rated carrying capacity of the tyres.
If the vehicle manufacturer has not specified the maximum towing mass, the maximum towing mass is:
One and a half times the unladen mass of the towing vehicle, provided that the trailer is fitted with brakes which are connected and in working order, or
The unladen mass of the towing vehicle if the trailer
does not require brakes
.