Xmas 2017

Suspension Modifications

Many vehicle owners feel that it is necessary to fit stronger springs to the back of their car or 4WD in order to tow a caravan. The justification is that the back of the car goes down when the caravan is lowered on the towball. If the vehicle is a few years old then the springs may be a worthwhile modification.

However if the only reason the suspension height alters is the weight of the van, then a weight distribution hitch is needed to take care of this, not stronger springs.

There are two cases where a suspension modification may be desirable or necessary. These involve additional loads in the vehicle that cause the vehicle height to reduce before the van is hitched on. If there is a constant additional load as, for example, in the case of an after-market LP gas conversion, then stronger springs may be needed to bring the vehicle back to its normal unladen height. In the case of occasional extra loads like camping gear then air-adjustable shock absorbers or air bags are most suitable. After the vehicle is loaded, air pressure can be adjusted to restore the original height. Air adjustable shock absorbers or airbags should not be used to compensate for weak springs or to support the weight of the caravan.

All shock absorbers on the towing vehicle should be in good condition to help prevent pitching or instability while towing. Good shock absorbers not only improve the handling of a vehicle but also increase tyre life.

Braking Systems

For many years now, caravans and camper trailers have been fitted with electric brakes. These braking systems are efficient and easy to maintain.

However, to enable the electric trailer brakes to function an electric brake controller must be installed in the towing vehicle. This is a job that should be left to an auto electrician or someone experienced with electrical systems in modern cars.

While there are several different types of electric brake controllers available, the most efficient ones have a feature known as motion sensing. This involves a pendulum that can determine exactly the amount of braking that the trailer has to do to ensure a smooth safe stop.

Once a brake controller is adjusted correctly the driver will be able to slow the car and caravan combination with the same force on the brake pedal as that needed to stop the car by itself.

Older caravans with over-ride hydraulic or mechanical brakes can be successfully converted to an electrical system. The cost can be easily justified on the basis of more efficient braking and improved resale value.

Sway Controls

Sway is the side to side movement of the rear of the caravan or camper trailer. This movement is sometimes referred to as “snaking” and results in complete loss of control. Because prevention is better than cure, sway controls should only be considered when all other factors causing the instability have been eliminated.
Some of the causes of sway are:

Poor caravan design
Incorrect ball height
Axle located too far forward
Unsuitable tow-vehicle
Under inflated tyres
Incorrect weight distribution

As a rule sway control equipment should only be fitted to larger caravans that may occasionally be affected by strong gusty wind.

Before purchasing any sway control equipment discuss your sway problems with people experienced in caravan towing. In some cases, particular types of equipment may be unsuitable. For example, some types are not recommended if override brakes are fitted.

Remember that even the best sway control equipment cannot be expected to, and should not, compensate for a towing vehicle that is too light, an unbalanced caravan or lack of a weight distribution hitch.

Weight & Size

With the trend towards smaller and lighter cars, the compatibility of the tow vehicle and caravan, in regard to weight and size, has become more important.

Weight:

Most vehicle manufacturers provide recommendation as to the maximum load that can be safely towed. These should not be exceeded and refer to the loaded weight of the trailer. Contents like water, gas, food, clothing and camping equipment will usually add at least another 300kg to the weight of an empty van. With larger tandem axle caravans this is likely to be 400-500kg
Newcomers to caravanning will find it beneficial to not tow more than the empty weight of the tow vehicle.

When a van is towed at a constant speed along a level road, weight is not an important factor. However, even a small, heavily loaded trailer can tax the available engine power when travelling through hilly terrain.

Size:

The smaller the frontal area of a caravan the less wind resistance is created. Therefore, less power is needed for towing. A camper trailer will be more economical to tow than a conventional caravan. However, some well designed hardtop caravans will be just as easy to pull as a pop top.

Many experienced caravanners prefer a conventional height van due to the convenience of being able to walk in without having to raise the roof or pull out bed ends as with a camper trailer. The deciding facts are probably the size of the towing vehicle, how often the van or camper is used, where it is stored and personal taste.

Tow Vehicle

Considering the importance of safety, the most suitable towing vehicle is one that is heavier than the caravan or trailer it tows and which has enough power to allow quick and safe passing manoeuvres.

As long as the manufacturer’s towing recommendations are not exceeded, modern passenger vehicles, including front wheel drives, are just as capable of towing a caravan or camper trailer.

While a vehicle with a manual gearbox is often preferred by drivers, many vehicle manufacturers recommend an automatic transmission for towing larger trailers or caravans.
One advantage is that the driver needs only to concentrate on the prevailing road conditions and not worry about whether the vehicle is in the correct gear. It also makes reversing much easier.
Some vehicles may need to be fitted with an auxiliary transmission oil cooler. Check with the car dealer or manufacturer if this applies to your vehicle.

Generally the type of suspension on the towing vehicle is not important as long as it is firm. Leaf springs are often considered more capable of supporting than coil springs but a good load distribution hitch will counteract the tendency of the rear of the vehicle to sag.
(refer to “Suspension Modifications” for information on coping with loads)

If the vehicle is fitted with self levelling suspension, the manufacturer’s recommendations regarding hitching up to a trailer must be followed. Unless a trailer is very small, a load distribution hitch is essential on self levelling suspension. Failing to follow such recommendations, or failing to use the correct towing equipment could result in damage to the vehicle’s suspension.

Towbars & Hitches

A towbar is to a car and caravan what glue is to two pieces of timber. Use the wrong glue and the timber will come apart, fit the wrong towbar to your vehicle and the caravan may not stay in place.

The capability of a towbar is often overestimated. Generally the only part that is visible is the tongue, lug or ballmount. While sometimes this appears to be quite strong, the actual mountings or thickness of material it is mounted into may leave much to be desired.

In relation to towbars there should be no compromise. Always purchase a recognised product that has a plate attached stating the maximum towing load. If a new vehicle is purchased with a towbar already fitted, do not assume that it matches the towing capabilities of the vehicle. Many towbars are only designed to tow small trailers and not heavily loaded caravans.

Before selecting a towbar, first determine the loaded weight of the caravan or camper. This can be done by placing the unit on a weighbridge or scales. Then purchase a towbar that can adequately cope with that load.

For larger caravans a heavy duty hitch receiver type towbar is usually required. These units mount onto the vehicle in several positions, enabling the load of the trailer to be spread over a wide area of the towing vehicle. As a result less stress is placed on any one part of the vehicle body than with a conventional towbar. This is most important on modern vehicles that do not use a chassis.

If in doubt to the best towbar for your vehicle and application, discuss your requirements with a towing equipment specialist. You will then be able to go away and have an enjoyable holiday, knowing that whatever you tow will stay with the car.