Whilst all above make a very valid point there is this concern that keeps coming up about "tow ball weight" in simple terms it does not apply or contribute to GCM, or effect the GVM of the vehicle.
Remember the weight of the load on the tow ball actually belongs to the trailer, so it's now not calculated as a load to the vehicle, but to it's towing weight.
The weight on your tow ball, as per RMS web site, is now calculated to tow bar manufacturers recommendation, where it use to be approx 200kg max, it's now left up the the tow bar manufacturers recommendation, although I did read somewhere that it still can't exceed XYZ, I could not find it on this new website of the RMS.
So GVM of my Xtra cab (as per rego ticket) is 2710 + 2500 towing capacity, total for both is 5210 Kg, so once the vehicle and trailer are coupled together the GVM for each becomes GCM in total.
The RMS could not have written it any more confusing if they tried, below is the extract.
Page 2 Draft Vehicle Standards Information No. 6 Rev 3
Roads and Traffic Authority
Vehicle Standards Information No. 18 Rev. 2, Oct 2003
RTA/Pub. 03.209 Cat. No. 45070598C
Further information:
www.rta.nsw.gov.auEmail:
tech-enq@rta.nsw.gov.auTel: 1300 137 302
Fax: (02) 9843 3821
RTA Technical Enquiries
PO Box 1120 PARRAMATTA NSW 2124
Mass Limits
Combinations including a towing vehicle with a GVM up to 4.5 tonnes
The laden mass of the trailer must not exceed:
• The capacity of the towing attachment (the towbar), or
• the maximum laden mass of the trailer, or
• the maximum towing mass specified by the manufacturer of the towing vehicle.
Where the manufacturer of the towing vehicle has not specified the maximum towing mass,
the following maximum towing mass applies:
• 1 1/2 times the unladen mass of the towing vehicle, providing the trailer is fitted with brakes that
are working properly, or
• the unladen mass of the towing vehicle.
The mass of any combination must not exceed:
• The towing vehicle’s Gross Combination Mass (GCM).