The Top 4 Common Causes of Caravan Sway and Instability
We are often asked by our customers, “What can I do when the caravan starts swaying while I am towing out on the open road?”
Our response is usually “Don’t set yourself up to FAIL in the first place. Do the basics correctly to minimise the risk and drive to the conditions presented to you. Our best advice is this: “The 100 kph sign is a speed limit, not an obligation.”
Caravan instability or sway - the simple things you need to consider and manage to minimise the occurrence of caravan and tow vehicle instability:
2. TYRE PRESSURE: The tyre pressures in both the caravan and the tow vehicle must be adequate for the load they are required to carry to promote a stable and enjoyable towing experience. Underinflated or overloaded tyres will tend to be spongy and will roll from side to side on their wheels. This makes for a twitchy, wollowy ride as well as accelerated or uneven tyre wear. Therefore, tyre pressures should be checked and adjusted in both the caravan and tow vehicle before setting off on any caravan adventure, even if it is only for the weekend. A good pressure gauge and air compressor are invaluable. Relevant vehicle tyre pressure information can be found on the sticker located inside the driver’s door jam on the tow vehicle. As for the caravan, many manufacturers have tyre pressure recommendations on the compliance plate. In the absence of available a tyre pressure recommendation, there are websites like that of G&S Chassis that feature a tyre pressure calculator. Utilising the calculator will allow you to work out the pressures for your specific application. Just remember too much tyre pressure is almost as bad as too little. In an overinflated state, the tyre sidewall does not act to minimise shocks from the road surface efficiently and can subsequently contribute to chassis and suspension components being cracked and damaged.
3. CARAVAN LOADING / BALL WEIGHT: In a modern caravan, it is generally recommended to maintain a ball weight between 7% and 12% of the caravan’s Aggrigate trailer mass. For example, on a 2500kg ATM caravan, the ball weight should fall between 175kg - 300kg.
This is necessary to maintain relative vehicle stability while towing. Loading the caravan correctly with the centre of gravity as low as possible and just over or in front of the caravan axle will go a long way to achieving this objective. i.e. that 40kg annex should probably go under the bed at the front of the caravan and not be stashed in the shower cubicle at the rear of the caravan. So, heavy items down low and centred over the axles or slightly forward with feather boas and cushions stored in the overhead cupboards. Got it! More than anything else do not be tempted to overload your caravan. Not only will your stability and control be compromised, but there are also some scary legal and insurance implications here as well. Know your weights and don’t fall into the trap. You should at some stage load your caravan like you are going on a trip with full water tanks as well as whatever you would load into the tow vehicle and have the whole lot weighed. You can do this at a public weighbridge, or an even better idea is to use one of the specific caravan weighing service. Caravan Towing Tuition now offer customers a towing course and weight study bundled service. All can be done on the same day. They will weigh each individual axle on the caravan and tow vehicle as well as from side to side. They can help you work out how best to load your rig to stay as safe and compliant.
Quick Definitions:-Ball weight - the downforce applied by the caravan drawbar onto the tow vehicle tow ball.Gross trailer mass (GTM) - the total weight that can be applied to the caravans axle group not including the ball weight.
4. BEING OVERTAKEN BY HEAVY VEHICLES:As it passes by, an overtaking truck will disturb the airflow over your caravan, often causing some short-lived instability. So, here is where a caravan reversing camera comes into its own, particularly if it is equipped with a microphone as many are. You will now hear a truck approaching you as it prepares to overtake your caravan. This does a couple of things for you: first, it alerts you to the oncoming truck and identifies the source of the instability. It further allows you to be ready and more importantly take evasive action by moving slightly to the left or right away from the passing truck. By increasing the gap between your caravan and the passing vehicle, you minimise the disturbance to the airflow over the caravan. Often this action can be the difference between experiencing a little sway or nothing at all.
SUMMARY. Managing these common causes for sway and instability will allow you to significantly reduce the occurrence of caravan sway, minimise the severity and often negate it altogether. This list is in no way exhaustive and is reflective of the advice we provide in our Caravan Towing and Reversing courses and of our own personal experience and practices utilised while towing.
Having said all of this, it is imperative that you know how you will react in a situation where all else has failed, and the caravan sway takes you out of your comfort zone.
A topic for another dayHappy caravanning…..