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The information on this page is in part reproduced for your convenience from the Caravan and Camping Club.
Safe towing primarily depends on a good match of car and caravan, but many other factors are important too, such as how you load your car and caravan and the maintenance and driving of the outfit. However, even with the perfect outfit there is still the possibility that a sudden side wind, unexpected pothole or passing a high-sided vehicle can create momentary instability. This is when a stabiliser can help.
The Caravan Club always advises caravanners to use a stabiliser, but not as a means of rectifying problems with a poorly-matched outfit or a badly-loaded caravan. It should be regarded as an extra safety precaution that will help if things go wrong.
Even the best loaded and balanced outfit can sometimes be affected by external factors that create unwanted movement, over which the driver has no control and it is then that a stabiliser can help.
There are basically two types of movement that a towed caravan can experience.
First is pitching – a vertical movement often experienced after going over a pot hole or sudden dip in the road. This feels alarming but generally will subside quickly when the unit is back on a level surface. It is however uncomfortable for the driver at the time.
Second is the lateral movement known technically as ‘yaw’, movement of the caravan from side to side relative to the car. According to circumstances this can either be a minor inconvenience that quickly subsides or a serious condition that, if left unchecked, can lead to the extremely dangerous loss of control. This is known as ‘snaking’.
There are now three main types of stabilising devices available – those that use a physical connection such as a blade between the car and caravan, those that are attached to the towball itself, and the latest electronically-assisted systems that use the caravan brakes to keep the unit in line. The first two types depend on some restriction or damping down of the caravan’s lateral movement to prevent the initial instability developing into something more serious and are therefore said to increase the critical speed at which instability occurs. The electronically-assisted systems work in a different way by operating the caravan brakes to pull the outfit into line once a set level of instability is detected.
The more stable the caravan is in the first place the less likely it is that a stability device will be needed. The following is not an exhaustive list of stabilisers, as there are other types on the market, but these are the most common.
The simple and inexpensive blade-type stabiliser was used with flangeball type towbars for many years and there is no doubt it can be effective. This system operates by using a metal leaf spring with a friction turntable at the car end to link the car’s towing bracket to the caravan’s drawbar (A-frame). As the caravan moves sideways relative to the car, the friction pads in the turntable act to resist this movement. The spring itself, being a strong piece of metal, will also provide resistance to vertical movements and thus help reduce pitching.
Generally the installation of this type of stabiliser is most suited to a standard fixed-flange towball, although sometimes a clamp can be fitted to a swan-neck towbar .
Simplicity, lack of ancillary equipment and needing little or no adjustment in use has made this a popular alternative to blade stabilisers, helped by many caravan manufacturers that now fit the item as standard to nearly all models in the range. They are however significantly more expensive than the traditional blade type and some claim that due to the small area of grip on the towball they are less effective.
The principle is simple – a special caravan hitch takes the place of the standard hitch and fits over a dry towball. Inside is a set of friction pads that press directly on to the towball and provide resistance to hitch rotation and hence trailer sideways movement. Such a stabiliser hitch will help keep the caravan in line when passed by heavy vehicles or in a cross wind. The latest AL-KO versions also have pads that will restrict vertical (pitching) movements as well.
AL-KO makes its AKS system available in various versions to suit the weight of the caravan, so make sure you buy the right one if fitting it yourself. There is a guide on the side of the device that shows when the pads need changing, which can be done as a DIY job, following the instructions provided.
It is vital when using this kind of stabiliser that the towball is completely free of grease or oil. Clean the ball with methylated spirit or similar to remove all traces of grease. A quick wipe over with a cloth is not enough. If you use your car to tow different types of trailer without such devices, you will always have to grease or degrease the ball each time you change.
The AL-KO stabiliser hitch is bigger than a standard hitch and cannot be used with a standard fixed flanged towball. A special extended neck towball must always be used with AL-KO stabiliser hitches, unless a swan-neck towball is used.
There can be a problem using an AL-KO stabiliser hitch with some vehicles that have spare wheels mounted on the rear door where the stabiliser handle operation is impeded by the presence of the spare wheel. A removeable handle is available from AL-KO at additional cost, which usually resolves the situation.
Caravans with BPW chassis, such as Elddis caravans, are fitted with a stabiliser hitch supplied by Winterhoff. This hitch uses the same principle of direct mounting to the towball, but it works with standard towballs as well as swan-necks. In theory you can fit an AL-KO version to an BPW chassis and a Winterhoff to an AL-KO chassis, but there are often difficulties with clearances especially with BPW’s gas-assisted handbrake. It is thus generally preferable when retro-fitting to use the stabiliser applicable to the chassis it was designed for. And neither should be fitted to any chassis that has the older 360 degree fully-rotating hitch, as the stabilising system will be less efficient. The Westfalia SSK unit is of a similar design and operating principle.
The towball mounted stabiliser hitch is the obvious choice for the growing number of towcars that are fitted with detachable towbars, as the stabiliser is fully part of the caravan and nothing needs to be attached to it from the car.
AL-KO introduced the ATC (Automatic Trailer Control) system – shown in demonstrator form above – for its chassis in 2007 , and the idea has taken off with many manufacturers fitting it as standard on some models. BPW has a similar system called iDC (Intelligent Drive Control) for use on its own chassis, such as those used by Elddis in the UK. Practical testing has proved that both these systems are effective in maintaining stability under severe conditions. These systems rely on sensors. When the sensors detect the sideways motion has gone beyond pre determined limits, they gently apply the caravan brakes until the unit straightens up. The systems draws power from the towcar’s electrics (12N or 13-pin) and features a self-test mode on start up and a status display on the caravan, which shows when it is ready to go. Neither has any indication in the towcar as to whether the system is working or faulty, but at least in the case of the iDC, it will revert to its start condition (brakes off) if there is a fault such as a blown fuse.
Both ATC and iDC can be factory fitted as options or are available for retro fit on most recent AL-KO or BPW chassis as appropriate for about £500. Both are intended to be used in conjunction with their manufacturers’ existing hitch stabilisers. For these systems it is essential that the towcar’s electrical supply system is able to supply sufficient power . In practice, experience has shown that failure of such systems is usually down to a blown fuse due to inadequate towbar wiring and the driver has no way of knowing about such a malfunction until the warning light on the caravan can be inspected.