Mark George, a senior accident investigator with more than four decades of experience (and a part-time grey nomad), explains why knowing your rig – and understanding its capabilities and limitations – are so important to staying safe on the road.
Survivors of caravan sway will tell you that the phenomenon is a very scary experience that can catch you by complete surprise and leave you wondering about what actually caused the incident.
Depending on the circumstances, trailer sway may often be unrecoverable, with devastating results, and whether or not you and your passengers happen to survive, as with any accident, is just a matter of timing and luck.
Caravan sway and the causes thereof are well documented within the caravan industry and scientific community.
From a laymen’s viewpoint, there are so many variables involved, that one can be easily overwhelmed in trying to understand the best preventative measures for your rig.
Generally, most caravan drivers know that incorrect load distribution, overloading, inappropriate tyres, tyre pressures, poor/inappropriate suspension, poor road conditions, the effects of wind, including buffeting from passing vehicles, and excessive travel speed, can all contribute to trailer sway.
Likewise, it is equally well known that there are many products readily available to help reduce the likelihood of trailer sway, such as load distribution hitches and anti-sway bars, or to arrest the effects thereof, such as Electronic Stability Control for caravans and Trailer Sway Control incorporated into some Vehicle Stability Control systems.
I like safety systems.
How you prepare your caravan and trailer is paramount to the safety of you, your passengers and other road users. Vehicle and trailer manufactures, and indeed many interested third parties, have gone to a lot of trouble to research and prepare easy-to-follow instructions for their particular products.
Follow your vehicle and trailer manufacturer’s instructions at all times. People who just hook-up and go are accidents waiting to happen.
Everyone’s rig will be different, but the must-knows are:
• The tare mass and gross vehicle mass (GVM) of both your caravan and tow vehicle
• Maximum towing capacity of your vehicle
• The gross combination mass (GCM) of your tow vehicle
• Maximum rated capacity of your towbar and coupling
• Maximum rated mass capacity of your tyres
• Maximum rated mass capacity of your axles
• The payload of your caravan and tow vehicle
• Load your caravan as recommended by the manufacturer, with the load bias forward of the axle. Subject to tow vehicle manufacturers’ specifications, you will want around 10% of the caravan’s loaded mass resting on the towball (invest in towball scales for your caravan)
• Consider using a load distribution hitch
• Consider using a sway control device if your total caravan mass is greater than your tow vehicle mass
• Do not exceed any of the above maximum capacities.
Next week, I will look at how important travelling at the correct speed is in staying safe on the road.
* Mark George is the Director and Principal Investigator of Accident Investigation Services Pty Ltd. He has been involved in accident investigation for 43 years, and is a current ACTAR Accredited Traffic Accident Reconstructionist.
We had a scary incedent on the Goulburn bypass 10 years ago sitting on 90K hit a small bump and suddenly we were using 3 lanes my wife applied the caravan brakes while I slowly eased off the speed . We stoped the sway and pulled into a rest area to check what happened . the suspension had jammed up on one of the shackels so suddenly we were on 3 wheels
Well done guys
I fitted the brake controller in the centre of the car so it could be used by either front seat passenger and when we had the sway if I had eased my grip on the steering wheel it would have torn it out of my hands . Now have rocker roller suspension and 15 thound k later not a single problem
Hi, Peter here i have been a caravanning for nearly 20 years but have been a heavy vehicle driver since1975, I find it very hard to listen to people with heavy vans in particular who claim that they don’t need load distribution bars because all they have to do is balance their weight evenly to keep their tow vehicle level with a 2t plus van attached. It is not possible to have the orrect ball weight & not add weight to the rear and take weight off the front wheels. All I can say is they have been lucky they haven’t experienced a serious sway situation. Research &investigation has proved that too little ball weight can & eventually will cause sway. I find these armchair experts give their opinions freely & dangerously to many new caravans when they ask for advice. I am also a believer in towing training & a towing endorsement on your licence. Well done very informative, keep up the good work.
I use a WDH and won’t tow without. I bought my first Roma caravan in 1987 and towed with an XE Fairmont complete with WDH. I purchased the Ezilift which at the time was Canadian owned and cheaper than the Reece and have used an Ezilift ever since. now tow a 22foot Jayco Sterling with a 2018 200 series GX cruiser.
Whist I can agree with some of your comments I have to disagree with the reasoning of the WDH. I see many people travelling with big vans on the back of duel cab utes. Whilst I agree with the notion that you cannot add weight to the rear without it taking weight off the front wheels, we really need to look into the vehicle specifications and limits. A Ute for example could have a 1tonne payload capacity, now if you put 1 tonne in the back of it without a trailer will it reduce the weight on the front axles? What about the sliding scales that many manufacturers have put into the weights calculations for towing, like if you apply 300kg ball weight you must reduce payload limits by 420kg. There are many factors that should be addressed when towing big vans. And I’m a firm believer in having the right tow vehicle for the trailer. Whilst I have researched WDH I find that people put a false sense of security on them, thinking that they are the silver bullet for a poor set up. Many people that use WDH don’t understand or even realise that using them can actually put them over the limits of their front axles, creating a negative effect.
I was going to replace the bushing on the springs and testing for movement, it was minimal. I undid the axles for the springs and could move the springs sideways by about 50mm. I feel movement that much could give a caravan the cause to sway.
Firstly we need to get this message out . I can not count the number of times I encounter caravan traveling with no regards to safety . One mayor point I believe should be compulsory is that all caravan sold should be delivered with a weigh bridge certificate and tow ball weight. This should not be a generic but the actual caravan with serial no and rego. We can then ,or least have starting weight point. I’m from the material/ forklift industry and weight have to be right. One last point , WDH bars are also used to hide poor set up
3 tons of van hanging off the back of a small dual cab ute is just asking for trouble when just some of these mentioned above come together. They were never designed to tow that much weight in the first place.
The biggest problem in controlling the sway regardless of what anti sway balance gadgets you might employ is the breaking ability of your caravan, How many caravaners actually do a break test, or know if their van is pulling up evenly on both sides? especially with electric breaks, I have had a few faulty electro magnetic actuators over the years and recently replaced a sized break adjusters.
I have a gravel drive way that I test the breaks on by fully turning the brake setting on at low speed touching the vehicle breaks then checking the drag marks in the gravel and if needed adjust the breaks until they are both even.
There is an inherent fault with these electric breaks in that there is no way you can without taking your eyes off the road and a hand off the wheel to actuate full breaking force to the caravan without applying the vehicle breaks, Yet you can answer the phone adjust radio volume change stations and engage cruise control all on your steering wheel without taking your eyes off the road or hands off the wheel. The accelerator is another forgotten option, hardly practical with the lag inherent on diesels even with turbos.
Applying the caravan breaks independently is the quickest way to rectify a sway, also handy on clay pans on dirt roads when your vehicle wont go in the direction you want it to go, it can help stop you ending up in a culvert.
With the old Vacuum breaks you only had to hit a lever down like a indicator lever just a bit longer on the opposite side to fully apply the caravan breaks.
I have seen many changes to caravans over the last fifty years not all well thought out or even practical, bling and gadgets rule, never mind safety.
Completely agree. The caravan industry is so backwards. Can’t believe that it is still mainly using drum brakes – vehicle manufacturers started replacing them in the 1960’s for the reasons that you note. We need hydraulic disc brakes and ABS. Not expensive when installed during manuacturing and so much safer.
Not sure how you get the idea that DSC is only needed if the van weight is greater than the tow vehicle? This makes no sense. DSC works effectively regardless of relative weights of the van V tow vehicle.
It also works much faster than the belief that a driver or passenger can react sufficiently quickly to use the manual van brake control. Research has shown that there is only a max of 4 sec to get the sway under control before it builds to a point where it cannot be stopped. Very few people have been found to be able to react sufficiently quickly to manege this.
Load management is not simply to ensure a 10% forward bias – the location of the weights in the van is just as important. Many people I have met think that they can balance the van by placing weight at opposite ends of the van in order to get the download weight correct. This of course is a fallacy. Placing weight at the rear of the van to reduce download weight simply introduces a high polar moment of inertia that creates van instability. The weight needs to be low and over the axles.
Many van manufacturers also do not understand this issue – trying to balance for example ill placed water tanks with say spare wheels hung out the back of the van.
The other issue that I think is worth noting is that there has been very little work done on the interactive effects of tow vehicle stability control and van stability control (or manual brake override). There is a potential here for the systems to be fighting each other. People who have advanced driving skills already complain about car DSC, AEB, etc overriding driver input – because the DSC, AEB is nearly always slower than a trained, alert driver – the driver corrects, then the DSC kicks in and so you end up with the driver and the DSC fighting to control the vehicle.