MAXIMISING STABILITY

Tom Olthoff looks at how you can maximise your rig’s stability with the rig equipment.

Words and photography by Tom Olthoff

Some caravanners are of the opinion that caravan or trailer sway is akin to a fait accompli, in other words, they are going to do it whether you like it or not. Of course, nothing is further from the truth yet many caravanners are making hard work of towing.

In Tom’s Workshop last year we explained why it is necessary to design and load a caravan so as to provide the correct balance. This generally means that about 10 percent of the total caravan weight is sitting on the towball. Check out http://www.candm.com.au/tom1.php.

But having the right balance is only the starting point. It is also necessary to add the right towing equipment and adjust this to provide the correct attitude of the car and van. I often liken the equipment that joins the trailer to the tow vehicle to insurance. And when it comes to towing equipment many caravanners are under-insured.

Lack of proper towing equipment can be result of poor advice, lack of appreciation as to what the benefits are or a sales person saying to the customer “see how it goes and if you have any problems come back and we’ll fit a hitch”.


There is no substitute when it comes to having the right towing equipment.

No one is going to take a new car or caravan out on the road without insurance, hoping that they won’t have an accident. We take out insurance for a ‘just in case’ situation. We insure our home in case it catches fire due to an electrical problem or if it is trashed after a break-in.

Similarly we insure the car so that when someone drives in to it or we run off the road during a lapse in concentration and cause some damage. The same applies to the van. When it comes to the towbar, load distributing equipment and perhaps an anti-sway device we should work on the premise that not all driving or towing conditions are perfect.

One day it may be blowing a gale, a road-train overtakes under less than ideal conditions, some cattle may amble across the road or a kangaroo carcass is lying in your path. Any of these and other conditions may need you to take swift evasive action. This is when you find out if you have the rig set up to offer maximum safety and stability.

THE TOWBAR

It should go without saying that the towbar must be suitable for the load being pulled. More importantly it must be the right design so as to allow the use of the appropriate load distributing equipment. Basically there are two types of the towbars, a standard towbar that has a bolt-on lug, tongue or ballmount and a ‘hitch receiver’ where the ballmount is held in place with a strong pin. The latter is also known as a square-hole towbar, Hayman Reese towbar (there are about six manufacturers of this type of towbar) and a heavy-duty towbar.

	Standard Towbar

	It is important to suit the right type of towbar to suit the load being towed.

Irrespective of the name given to it, it is the rating or towing capacity of the towbar that is important. For light trailers or any that have a ball load that is less than 130kg, a towbar with a bolt on lug is fine, the reason being that there is no load distributing equipment available with a higher capacity than 130kg that can be attached to a simple flat tongue.

This type of ball mount can handle ball loads up to about 130kg with the right levelling equipment.

For trailers with higher ball loads, a hitch receiver is required so that the required levelling equipment can be fitted. It should be noted that some car manufacturers recommend that a hitch receiver is used for lower ball loads. For example, some Subaru products requires a 50mm square hitch receiver to be fitted when the ball load exceeds 90kg to enable a load distributing hitch to be used.

While some may consider that a weight distribution hitch on a rig such as this is overkill, it certainly adds to the towing safety when the ball load is 110kg which is enough to affect the attitude of a car.
On the other end of the scale some manufacturers suggest that a ‘standard towbar is suitable up to a towing load of 1600kg although there is no way of adequately coping with a ball load of 160kg or thereabouts.

WEIGHT DISTRIBUTING OR LOAD LEVELLING HITCH

A weight distributing hitch (we’ll refer to it as a WDH) is generally a misunderstood piece of equipment. To understand its function we need to appreciate what happen to a tow vehicle when a vertical load is placed on a towball. Most will agree that the back of a car goes down when ever a trailer is hitched on. What is not always appreciated is that as the back goes down, the front rises. Just think of a seesaw but instead of the pivot point being in the centre, imaging it being off to one end.

A WDH is often the key to safe towing

A car is like a seesaw when a load is applied to the towball.

We now have two problems. Not only is the rear axle carrying an excessive amount of load, there is less contact between the front tyres and the road. This is a most undesirable situation as the amount of tyre contact of the front wheels affects the steering and braking. And if it is a front wheel drive car, also the traction.

With the van hitched to the car there is an extra 200kg on the rear axle. This is made up of the 150kg ball load plus 50kg transferred from the front axle.

Some people, often 4WD owners, believe that the fix consists of simply fitting stronger springs or air bags to the rear suspension. All this does is raise the rear and leaves the front of the vehicle higher than before the trailer was hitched on. Similarly some that own cars with self-levelling suspension mistakenly believe that takes care of the load on the towball. Self-levelling suspension is designed to maintain a set vehicle height with occupants and luggage on board. Not when there is a vertical load a considerable distance behind the rear axle.

Relying on self-levelling suspension to take care of the load on the towball can result in expensive repairs to the air compressor and/or airbags.

ANTI-SWAY EQUIPMENT

This is unfortunately another misunderstood piece of equipment. Anti-sway equipment has nothing to do with a weight distributing hitch (WDH) although some believe that a WDH cures sway or instability. This could be true if sway was caused by the tow vehicle going along with a nose-up attitude. But when a trailer wags its tail when being passed by a large truck or a strong gust of wind then something other than a WDH may be required.

It should be stressed that anti-sway equipment should not be added to a rig that behaves in an unstable manner most of the time or when going a bit faster than normal. The first step in these situations is to find the basic cause. This could be incorrect loading, wrong type of towing equipment, incompatible outfit or adopting the wrong towing skills.

Special anti-sway equipment should be considered as additional safety or insurance. There are three general types. There is a coupling with spring loaded pads that clamp on to the towball, a sliding friction device that bolts on to the side of the drawbar and attaches to the ball mount and a ‘dual-cam’ anti-sway unit that is used in conjunction with a Hayman Reese weight distributing hitch. The latter has a useful self-centring function which not only prevents sideways movement, it also brings the trailer back to a straight ahead position.

	The Alko 3000 stabilisers have a mechanism that allows the coupling to tightly grip the towball and reduce swaying tendencies.

	A friction sway control can be added to most outfits

	A dual cam sway control has a self-centering action that helps stability.

SUMMARY

There is really no substitute for having the right towing equipment. Apart from making sure that the car and van stay together, it also reduces the stresses that can be associated with towing. Any well set-up car-trailer combination will tow in a stable manner without causing any concerns. But sadly there are many excellent caravans being towed by equally excellent towing vehicles that are an accident waiting to happen due to the lack of the right towing equipment.

Having the right towbar, weight distributing hitch and, if towing a large van, an anti-sway device should be seen as being just as important as settling for a car and van that has appeal. Don’t wait until something goes wrong to make the investment. Do it all to start with and you will be able to handle any situation that may arise and be ready, just-in-case there is something unexpected.

Even a 4WD with a single axle pop-top can become difficult to handle without a weight distributing hitch.

A small van with a high ball load due to the axle being located towards the rear also needs a weight distributing hitch