Choosing a Tow Vehicle

NOT a recommended tow vehicle for this caravan... - Pic: From 'Free to Roam' by John Swerder
NOT a recommended tow vehicle for this caravan...

Pic: From 'Free to Roam' by John Swerder

Choosing a tow vehicle - Tow Vehicle Capacities

There are four key vehicle specifications that you need to know when choosing a tow vehicle. These are not always easy to find, so RV Books has provided a list of towing specifications for some popular tow vehicles below.

It is important that your caravan or trailer does not exceed ANY of these specifications. These are:

  • Maximum Towing Capacity - this is the maximum mass that a tow vehicle may tow. Tow vehicle manufacturers normally stipulate two towing capacities - for trailers that are braked and unbraked. Braked trailer towing capacity is generally much higher than unbraked, because a braked trailer's brakes help to stop the trailer and reduce the forces imposed by the trailer on the tow vehicle.
  • Maximum Towball Mass - this is the maximum amount of downwards force that may be placed by the trailer on the towball of the tow vehicle. This trips up some new buyers, because the required downwards force of the trailer (usually about 10% of the trailer's laden weight) can exceed the (sometimes modest) towball mass limit of the tow vehicle.
  • Gross Vehicle Mass ('GVM') - this is the maximum permissible laden mass of the tow vehicle including all optional equipment, luggage, passengers AND any downward force imposed by the trailer on the towball. When towing, you must make sure that towball mass is taken into account when loading your tow vehicle.
  • Gross Combined Mass ('GCM') - this is the maximum permissible laden mass of the tow vehicle AND trailer combined. See 'The GCM Trap' below.

Note re towbars - If, when choosing a tow vehicle - it has a towbar fitted that was not manufactured and installed by the tow vehicle manufacturer, check its maximum towing capacity carefully. It could be different (and possibly lower) than the maximum towing capacity of the tow vehicle. If so, this lower limit is likely to be your maximum towing capacity for that tow vehicle.

Choosing a Tow Vehicle - Can I Tow to Maximum Towing Limits?

We strongly recommend against towing up to your limits.

Tow vehicle maximum towing capacities are derived from manufacturers’ towing tests that, in effect, pull a fixed load at the end of a cable and ensure the ability to restart on a steep hill. They do not take into account towing dynamics such as the effects of trailer dimensions, side forces, load distribution, overhung hitches, tyre types and pressures or suspension, chassis, towbar and hitch construction.

For this reason it is strongly recommended that laden trailer weights are well below the maximum towing capacity of the tow vehicle and ideally 80% of the tow vehicle’s own laden weight.

Read more about recommended tow vehicle to trailer weight ratios here.

Choosing a Tow Vehicle - the GCM Trap

GCM, or Gross Combined Mass, is the maximum permissible laden weight of tow vehicle and trailer combined.

You would have thought that a tow vehicle's GCM would be the same as its maximum towing capacity plus the GVM, or Gross Vehicle Mass, of the tow vehicle.

But with some Australian tow vehicles (in particular utes), this is not the case. The total of maximum towing capacity plus GVM in these cases exceeds GCM, sometimes by several hundred kilograms. Why? Because a maximum towing capacity of 3500 kg is seen as desirable by many tow vehicle manufacturers and this headline number is used to attract buyers. But with a fully loaded tow vehicle the effective towing capacity is much less, as dictated by the tow vehicle's GCM.

Tow vehicles where maximum towing capacity plus GVM exceeds GCM are highlighted in grey in the table below. For these vehicles either maximum towing capacity and/or GVM must be reduced by the excess amount in order to meet GCM.

Choosing a Tow Vehicle - Tow Capacity Table

Below are the key towing capacities of some popular Australian tow vehicles. The maximum towing capacity show is braked trailer capacity only - if your trailer does not have brakes, please refer to the tow vehicle manufacturer to ascertain each vehicle's unbraked towing capacity. Refer above for definitions of GVM and GCM.


Notes

  1. Specifications are for Australian vehicles only and are subject to change. Check with manufacturer before making a purchasing decision.
  2. The table is a general guide only. Towing specifications may vary within model ranges and depends on engine size, engine type and transmission type.
  3. Data relates to current (2018) models only. Older or newer models may have different towing capacities.
  4. Maximum braked towing capacities include heavy duty towing options where available.
  5. Where a weight range is shown, towing capacity varies with trailer mass.
  6. Sources: manufacturer's websites, redbook.com.au, carsales.com.au.

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