On-Vehicle Mass

GVM – Gross Vehicle Mass is the accepted safe, maximum allowable total mass of a fully loaded motor vehicle. It consists of the kerb mass (mass of the vehicle itself with all fluids) plus the payload – see description below.

Payload – A vehicles’ payload is the maximum capacity of the vehicle for the carriage of all non-standard items including the vehicles body (tray, tipper, van etc), the cargo itself, occupants and optional equipment and accessories (bull bars, spot lights, roof racks, tow bars etc)

Kerb Mass – A vehicles kerb mass is the mass of the vehicle in running order, unoccupied and unladen with all fluid reservoirs filled to their nominated capacity. All standard vehicle equipment is also included in the kerb mass.

Maximum Available Payload – The available payload is calculated by subtracting from the vehicles GVM, the vehicles kerb mass, the total weight of the occupants, the weight of any fitted options (bull bar, tow bar, spot lights etc) and the weight of the fitted body (tray, van, tipper). This remaining figure is the maximum allowable weight of the cargo which is to be placed upon the vehicle.

This calculator link can help you discover your maximum available payload.

Axle Weights

The final point of interest in vehicle weight determination is axle weights. The axle weight is the maximum load that can be placed over each axle on the vehicle. Each vehicle will normally specify their front and rear axle weight in the product specification sheet.

In some vehicles the rear axle is not rated sufficiently to take the entire weight of the payload by itself. In these instances some weight will need to be re-distributed over the front axle, this is commonly done by using a rack arrangement. Be sure to check your individual vehicles specification sheet to ensure that your payload can be supported on the desired areas of the vehicle.


Maximum Towing Capacity

Calculating the towing capacity is relatively straight forward once you have calculated your maximum allowable payload.

Maximum towing capacity – Each vehicle will have a maximum towing capacity with braked an un-braked trailers. This is the total weight the vehicle can legally tow and it includes the physical weight of the trailer as well as the weight of the cargo placed upon it.

Things can become complicated when a vehicle, which can tow a given amount when unladen, attempts to tow a trailer with payload weight also on the body. It does not matter if the vehicle can tow a given weight in a particular situation; it cannot, at any time, exceed its nominated GCM.

GCM – Gross Combination Mass is the accepted safe, maximum allowable total mass of a fully loaded motor vehicle and all of its trailers. A graphical representation of this can be seen below.