What is a stabiliser?

Towing stabilisers act as control devices that alter or restrict vertical and lateral articulation between the trailer/caravan and the towing vehicle. The inherent stability is not increased by this device.

What causes vertical instability?

Vertical instability or pitching occurs on uneven or undulating roads. Humps such as bridges, any sudden dips, pot holes and even drain covers can unsettle your outfit. The likelihood of pitching increases if the centre of gravity is too high. Other risk factors include an incorrect nose load or worn rear suspension.

What causes lateral instability?

Lateral stability, commonly known as snaking or swaying, occurs for a number of reasons. Larger vehicles passing can cause a suction effect. Faster vehicles passing can cause a change in pressure. Unexpected changes in road camber and sudden side winds can all cause snaking or swaying. The risk of snaking is further increased by a poorly matched outfit or a high centre of gravity.

Why do I need a stabiliser?

There is nothing pleasant about the sensation of a trailer/ caravan snaking or swaying behind your towing vehicle! If snaking or swaying becomes uncontrollable the results can be devastating. A driver could lose control of the steering on their towing vehicle. Many roll-overs and other accidents have been caused in this way.

What is snaking?

A trailer or caravan can act like a pendulum when it starts to swing behind a vehicle, this causes a situation of instability to occur which is known as snaking. Little energy is required to maintain the movement. If the oscillations reach the outfit’s natural resonance the snaking will increase to such an extent that a loss of control is inevitable. This would certainly result in a crash!

Has anyone researched this phenomenon?

Considerable effort has been channelled into understanding the phenomenon of snaking. The Caravan Club has overseen and sponsored a number of extensive projects at Bath University. The academic mentor and leader of these projects is Dr J Darling who is renowned for his in-depth knowledge on the subject .

How can I improve the inherent stability of a trailer or caravan?

Increasing nose load or the static vertical load applied to the towball will reduce the risk of instability in the towing vehicle or trailer. This has been irrefutably proven. Therefore, increasing the nose load to the vehicle or trailer’s maximum (whichever is the lowest) permitted amount is strongly recommended. A well matched and balanced outfit is also essential.

How is balancing an outfit achieved?

The likelihood of instability increases as the distance of the axle from the centre of mass also increases. The weight must be centralised laterally, longitudinally and vertically to achieve the correct nose load. This will balance the outfit. If an outfit is unbalanced it is also unstable. A low centre of gravity that is slightly forward of the axle is desirable.

What does matching your outfit mean?

You will often hear the term ‘matching your outfit’ used by towing and caravan organisations. This is simply selecting the optimal caravan/ trailer and vehicle combination. The maximum caravan weight and nose load along with the vehicle’s kerb weight and towing capacity are used to calculate this. Caravanning organisations are a good source of information on matching outfits.

Which caravans are the most stable?

Caravans or trailers with two or more axles are more stable, so these are the preferred option for many. Single axle caravans or trailers have less resistance when it comes to changing direction.

How can I increase my caravan’s stability?

The trailer’s mass should be as low as possible in order to reduce the likelihood of initialising instability. It is necessary to check the tyre pressures on the vehicle and caravan to the specifications of the manufacturer before each use.

How can my caravan’s handling be improved?

You will often find that caravans and trailers come complete with damper mounting points but these are not standard. Fitting a caravan or trailer with dampers is another way to increase stability.

Do diffusers and spoilers increase the stability of a caravan?

These devices assist with aerodynamics but the effect on stability is negligible.

Would fitting a stabiliser improve stability?

Fitting stabilisers will not affect the inherent instability of a vehicle or trailer. A well designed stabiliser will, however, suppress the pendulum like motion of a caravan or trailer. This could potentially prevent a moderate degree of instability. It is important to note that stabilisers should not be your only solution to the problem of instability.

Can I increase stability by changing my towball height?

Altering the towball height does not have any direct or significant effect on stability. However, if the nose load is affected by the height this is an exception. A good example of this is when a twin axle caravan/trailer with a high coupling height is used in conjunction with a low towball height.

When I tow the nose on my outfit is down, how safe is this?

It is recommended that you aim for a nose down attitude with a single axle trailer because the rear vehicle lift will be reduced. This is important during heavy braking as it reduces the risk of jack-knifing. A level outfit is desirable for twin axles.

Is the stability affected by the type of towbar?

 

Towbars do not affect a trailer’s stability directly. There is little in the way of elastic deformation or lateral deflection in the actual towbar when compared to the suspension and tyre movements of the towing vehicle and trailer.

Is there anything I can do to my vehicle to increase stability?

There are ways to increase stability that involve adjusting different variables:
• Tyres: Tyres with stiffer walls that run towards the high end of the recommended range of pressure help to dampen instability
• Springs: Potential instability is reduced by stiffer springs. Leaf springs on towing vehicles result in improved performance. However, changing the spring rating is also an option , and you can use suspension aids or stiffer springs for this
• Dampers: Shock absorbers or stiffer dampers will also reduce the likelihood of instability in the trailer. Changing to a stiffer damper setting will improve matters
Trailer instability can be significantly improved by implementing one or more of these adjustments. It is important to bear in mind that this does not necessarily confirm that the towing vehicle is responsible for the instability.

Is it necessary to use a stabiliser?

The jury is still out on this one. On one hand a correctly loaded and well matched outfit should not need a stabiliser. However, unexpected circumstances and external forces can negatively impact upon an outfit’s stability. These unknown factors could come into play at any time, so some drivers prefer to use a stabiliser, even if purely for peace of mind and confidence.