Steady and true: Towing essentials
Know the essentials of legal and safe towing.
EVEN THOUGH WE are supposed to have national towing specifications, it seems there are still some variations across the country. What is legal in one state may in fact be outside the law in other jurisdictions.
There is always a safe limit to the weight a motor vehicle can haul, and that limit is set by the vehicle manufacturer. Every car has this limit printed on its compliance plate, and it’s usually in the manufacturer’s driver handbook, too.
In addition to this limitation, the capacity of the towbar, or any part of its fittings (ball, coupling, safety chains), must not be exceeded. According to the Uniform Towing Laws (1998), "Motor vehicles of GVM (Gross Vehicle Mass) not exceeding 4.5t must not, unless with the approval of a specified authority, tow a trailer with a total mass (including load) exceeding the figure shown on the compliance plate."
At the time of manufacture, RV builders are required to affix a compliance plate to every caravan stating its empty weight (Tare) and laden weight limit (Aggregate Trailer Mass – ATM).
The legal responsibility falls on the operator of the tow vehicle and caravan combination to make sure both units stay within legal weights, and that the combined weight of the rig does not exceed the stated legal Gross Combined Mass (GCM) of the caravan and tow vehicle.
Some particularly old caravans may not have a compliance plate, so you will need to ask the registering authority if they have details of its weight, or take the unit to a public weighbridge. But if you still plan on purchasing a vintage van built before some of these legal requirements were introduced, you might not want to proceed until you have a weighbridge ticket confirming the weight.
In addition to stating the maximum mass the vehicle is permitted to tow, vehicle manufacturers are increasingly specifying a vertical load limit that is permitted on the rear of the tow vehicle.
In fact, more and more vehicle manufacturers are providing maximum load capacities per axle.
This figure is provided because the behavior of an overloaded vehicle is unpredictable. Most manufacturers now issue a statement of axle limits, i.e., the maximum load any axle can handle. Your rear axle load limit, in particular, should be observed.
When considering what size or weight caravan your vehicle is allowed to tow, your calculations must include the weight of whatever goods are placed in the back of the tow vehicle (luggage, food, refrigerator, spare wheel, etc.), plus the weight placed on the towball by the caravan or trailer.
All this adds up to mean your selection of a caravan should be limited to rigs falling within the stated weight limits of the tow vehicle.
TOW VEHICLE CAPACITIES
Nowadays, all towbars and associated items must have their capacities stamped on them. The lowest capacity item in the various towing components sets the limit for the entire rig. So even if your truck is permitted to haul 4000kg, a 3500kg towbar sets a limit of 3500kg. To ensure you are legal, you need to know the capacity of the towing equipment fitted to the vehicle and the maximum trailer mass specified by the vehicle manufacturer. These will be listed in the vehicle’s owner handbook.
In the event the manufacturer has not specified a total towing mass, the limit is the equivalent to the unladen mass of the tow vehicle where the trailer has no brakes, and 1.5 times the unladen mass if the trailer has brakes.
It is your responsibility, not the salesperson’s, to ensure a caravan matches your tow vehicle.
The weight at the front wheels of the tow vehicle is especially important. Most people would understand that a large load at the back of the car can create a see-saw effect, and inadequate front weight adversely affects steering and braking because the wheels cannot grip as well as they should.
A simple way to check front-end load is to carefully measure the distance from the ground to the top of the front wheel arch when the tow vehicle is unloaded and not connected to your van. Then connect the (fully loaded) van and measure the wheel arch height again. If it’s the same, the tow vehicle is correctly set up, but if the height is greater you need to adjust the weight distribution gear to restore the ground-to-wheel arch measurement to the same height as when unladen.
The law also requires the tow vehicle driver to be able to see vehicles behind their rig. This is most often managed by using towing mirrors that extend out to allow a greater range of sight behind the caravan. Without these mirrors in place, the driver may be issued a fine or other traffic infringement notice.
WORDS Lloyd Junor
Source: Caravan World Jan 2012