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Key points for safe and legal A-frame towing.

We’ve had requests to clarify the situation when A-frame towing a car behind a motorhome. In this assembly of seven different countries called the ‘Commonwealth of Australia’ that’s not a simple job.

Each state and territory has different laws regarding towing vehicles behind trucks or motorhomes, so if you plan to flat-tow a vehicle all around Australia you’ll have to make sure the combination will be legal everywhere.

Some states enforce the ‘3.5:1 ratio’ rule, whereby the towing vehicle must have a tare mass – notgross vehicle mass (GVM) – that is 3.5 times the mass of the towed vehicle. That means a towed vehicle with a mass of 1200kg can be coupled to a motorhome or truck with a tare of 4200kg.

Other jurisdictions insist that any towed vehicle that has GVM over 750kg must have a braking system that is activated by the driver of the towing vehicle. (In any case, all towing vehicle manufacturers require trailers over 750kg to be braked.)

For a nationwide ‘best fit’ you need to select a flat-towed vehicle that complies with the 3.5:1 ratio rule, as well as having a connection that provides brake pedal actuation.

It’s also likely that the motorhome, A-frame and towed vehicle assembly will need inspection by a certifier, before a certificate of approval is issued.

There are several different types of A-frame and the simplest use mechanical override braking, with a cable link between the override coupling and the towed vehicle’s brake pedal. The cable is fitted through the firewall, linked to the brake pedal and is connected to the towing vehicle when the A-frame is hooked up.

Override braking is permitted on towed vehicles up to 2000kg mass.

When the A-frame vehicle is being driven, brake pedal power is normally boosted by vacuum pressure, but when the vehicle is being towed and the engine isn’t running there’s no vacuum being generated. Some A-frame braking kits employ a pressure cylinder to push hard on the brake pedal, so vacuum assistance
isn’t needed and others use an electric vacuum pump to maintain brake booster power.

Obviously, the towing vehicle’s manufacturer-rated gross combination mass (GCM) must not be exceeded and its tow bar must be rated to haul the towed vehicle’s GVM.


Towed vehicle options

It’s important to liaise with your preferred A-frame supplier before deciding on the towed vehicle make and model. Many manual 2WD vehicles can be towed, but few automatics can.

Not all vehicles have A-frame base plates that attach to the towed vehicle. It is possible to have a custom base plate made, but at additional cost.

4WDs are popular towed vehicles, allowing off-road excursions away from a motorhome base, but some cannot be A-frame towed – particularly some full-time or on-demand 4WD types and automatics.

It’s not possible to generalise across makes or models. For example, most Suzuki Grand Vitara automatics can be A-frame towed, because there’s a neutral (N) position in the transfer case that isolates the main transmission, but the 2006 three-door can’t be A-frame towed.

Some Jimnys can be A-frame towed and some need a transmission modification.

Whatever car make is towed, it should be protected against a barrage of stones by a mesh guard.






























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