One of the scariest things for a caravanner to experience is caravan sway, also known as ‘snaking.’
While caravan sway is actually quite normal and the van usually will pull itself back into line behind the tow vehicle, there are some scenarios where that swaying can pick up momentum and go the other way.
Even before hitting the road, it’s important to make sure you’ve ticked off all of the preventative measures to help stop caravan sway while towing.
It’s also just as important to educate yourself on how to react if you find yourself in a situation where the caravan is beginning to pick up sway behind you.
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What Causes Caravan Sway?
There are a combination of factors that can cause caravan sway and while some can be beyond your control, others will help to stop caravan sway on the road.
Here are the common causes of caravan sway.
Incorrectly Loaded Caravan
Load distribution when packing the caravan is a vital factor in keeping your trailer balanced and correctly weighted for towing.
The common rule of thumb is to pack the heaviest items over the axles in the middle, which is the pivotal point and designed to “carry” the load.
If a caravan is overloaded at the ends, it will create ‘Yaw Inertia,’ also known as “sway” or “snaking.”
Having the two heaviest sections at the farthest points from the pivotal point (the axles) can increase caravan sway. When that happens, it tends to increase in oscillation (the back-and-forth rhythm) rather than being pulled into line by the force of the towing vehicle.
In other words, having too much weight at the ends of the caravan (rather than in the middle) will actually cause the caravan to pick up momentum if it starts to sway. Once that swaying gets to a certain point, it becomes virtually impossible for the driver to control it.
Tyre Pressure Being Too High or Too Low
The tyres are the only point of contact between the caravan and the moving ground below. Having the correct tyre pressure is very important for ensuring that a caravan doesn’t unnecessarily begin to sway.
If the tyre pressure is too high, it will cause the wheels to bounce up and down more along the road, which can result in caravan sway. It could be as simple as hitting a bump in the road, which creates back-and-forth movement in the caravan and off she goes. When the caravan is in the air (even if just for a millisecond), you have zero control of it.
On top of that, having more pressure than you need will cause the centre of your tyres to wear out quicker.
Caravan Nose Being Too Heavy or Too Light
Tow ball weight (TBW) is the amount of weight that gets transferred off the front (nose) of the caravan and onto the rear of the tow vehicle when it’s hitched up.
It’s important to have the right amount of tow ball weight so that the front of the caravan isn’t too heavy or too light.
- TBW that’s too heavy – takes weight off the tow vehicle’s front wheels and compromises braking & steering
- TBW that’s too light – causes the caravan to be ‘nose up’ & increases the chance of swaying
Speeding
Driving too fast is one of the most common causes of caravans swaying. The scariest part is that once the swaying motion kicks in, handling it at high speed is much more difficult and can more easily result in jackknifing and rolling.
Overtaking or Being Overtaken by Trucks
Another factor here is the massive pressure of air around the nose and down the side of a truck as they’re travelling at speed along a highway.
If a truck overtakes a caravan (or vice-versa) that vortex of air can create two effects.
The first is where the air pressure pulls the caravanner towards the truck, which can occur in the space down the side of the truck, but behind the cab. The second is where the ‘bow wave’ at the front of the truck pushes the caravanner away from the truck.
Whether the caravanner overtakes the truck or the truck overtakes the caravan, the push-pull of air pressure can cause the caravan to pick up some sway motion.
Most times, you’ll just feel some tugs from the van behind you and while maintaining the same level of acceleration (without touching the brakes), the caravan will straighten itself out.
However, the faster you’re going, the quicker sway can potentially gain momentum meaning the higher the risk of losing control.
Half-empty Water Tanks
Towing a caravan with half-empty water tanks creates ‘water slosh’ and instability, causing the caravan to sway with the water movement.
As you’re driving, any water left in the tanks (unless full or empty) will swish backwards and forwards and side-to-side with every movement. The momentum of the waves of water can pick up as you brake, turn a corner or go over a bump in the road.
You should never tow a caravan with half-empty caravan tanks. They either need to be full OR empty, but not in between.
Heavy Side Winds
If the weather conditions are extremely windy when you’re planning on travelling, it might be wise to postpone your departure until the wind settles down or wait for another day.
Having high wind hitting the side of your caravan can dramatically increase the chances of caravan sway and this force of nature is beyond your control. If you find yourself in this situation it’s best to reduce your speed or pull over until it’s safe to hit the road again.
How to Stop Caravan Sway
When looking at how to stop caravan sway, there are many strategic things you can do to reduce the likelihood of ‘snaking’ while driving.
Here are some tips for reducing the chance of caravan sway.
Correct Weight Distribution
To correctly distribute the weight throughout your caravan, it helps to think of the van as a see-saw. If you pack too many heavy items towards the front or rear, you’ll end up with a caravan that is either “nose up” or “nose down.”
How to correctly load a caravan:
- HEAVY ITEMS – Over the axles
- MEDIUM WEIGHT ITEMS – Down low (under window height) & towards the middle
- LIGHTWEIGHT ITEMS – Up high & at the ends
- Pack evenly across both sides (left to right)
Correct Tyre Pressure
Having the correct pressure in your caravan’s tyres will have a massive impact on how the van rides behind the tow vehicle. It’s also important to ensure that all of your tyres are pumped up evenly.
Below is the calculation for working out your correct caravan tyre pressure.
Caravan Tyre Pressure Formula
How to Calculate Caravan Tyre Pressure:
Max Tyre Pressure (cold) ➗ Tyre Load Rating (kg) ✖️ Actual Load on Each Tyre
🟰 Correct Inflation Pressure
| Or, use the Caravan Tyre Pressure Calculator → |
Check Your Pressure Using the ‘PSI Rule’
When checking your caravan tyre pressure there should be a psi increase between when your tyres are cold and warm (from driving).
Psi increase when tyres warm up should be…
- 4 psi for Road Tyres
- 6 psi for 4WD & Light Truck Tyres
Checking tyre pressure with the ‘PSI Rule:’
- Make sure your caravan tyres are cold (not driven for at least 2 hours)
- Inflate tyres to the correct cold pressure
- Tow the caravan fully-loaded for 100 km (preferably on the highway)
- Measure ‘hot inflation pressure’ immediately
If the…
- Hot inflation increase was less than 4 – 6 psi = cold tyre pressure too high (deflate tyres a little)
- Hot inflation increase was more than 4 – 6 psi = cold tyre pressure too low (inflate tyres a bit)
Correct Tow Ball Weight
The tow ball weight of a caravan is a fluid figure that will change every time you add, subtract or shift the caravan’s load.
The accepted TBW in Australia is around 8 – 12% of the caravan’s fully loaded weight (ATM) or a maximum of 350 kg – whichever is lower.
The easiest way to ensure you’re always within your correct tow ball weight range is to get yourself a set of Ball Weight Scales.
Whenever your load shifts or changes (e.g. your water tanks empty out or you add in extra luggage), you can put the Ball Weight Scales under the caravan hitch to see exactly what your current TBW is.
For two more ways to measure tow ball weight, check out the post below.
Watch Your Speed
When towing a caravan, maintaining a safe speed is not always as simple as following the speed limit signs.
While it’s important to never exceed the speed limit, in some situations you may find that even that is too fast. Depending on the weather and road conditions, you may need to travel under the speed limit in order to remain in full control of your caravan.
Keep in mind that if travelling under the speed limit is holding up other drivers, you may need to pull over to let people pass or seek an alternate route if safety is an issue.
Fill Your Water Tanks
Towing with full water tanks adds a lot of extra weight down low in your caravan and over the axles (which is the ideal position for weight). This effectively lowers the centre of gravity, which increases the caravan’s stability and helps to stop caravan sway.
However, if you are already at your maximum caravan weight limits without having any water onboard, you will not be able to tow with full water tanks.
It’s important to know all of your caravan weights first, before filling up the water tanks for travel.
For more about towing with full water tanks, check out the post below.
Electronic Stability Control (ESC)
If you want to be able to maintain extra towing stability on the road, consider fitting Electronic Stability Control (ESC).
ESC automatically responds to the driving behaviour of the caravan by monitoring for any dangerous side-to-side movements and taking preventative action immediately. It will automatically apply the caravan’s electric brakes in order to keep the caravan stable on the road and stop caravan sway where possible.
ESC by AL-KO:
ESC brakes all wheels on a caravan simultaneously as soon as a dangerous sideways movement is detected – and holds them on to wipe off speed and stopping distance in the shortest possible time for maximum control.
This maintains the line and stability of the car and caravan allowing you to perform an emergency avoidance manoeuvre. Your car and caravan operate as one – there’s no jack-knifing – and you’re back on your side of the road with a potential disaster behind you.
What to Do if You Feel Your Caravan Swaying
Most caravanners will have experiences where they’ve felt the caravan sway behind them. But, the most important thing is how you actually react in that moment.
WHAT TO DO IF YOUR CARAVAN STARTS SWAYING:
- Do Not Hit the Brakes – Applying heaving braking through the tow vehicle will cause a sudden change in movement.
- Steer as Little as Possible – Quick steering will create sudden movements, which will make things worse.
- Reduce Acceleration or Maintain Speed – Either maintaining your speed or naturally allowing the vehicle to slow down can reduce the caravan’s back-and-forth movements.
- Gently Apply the Caravan Brakes – Manually and gradually apply the caravan electric brakes (if fitted) to help slow the swaying. ECS will do this automatically for you.
- If Going Uphill – Accelerate gently until swaying stops, then slow down and continue at a slower speed.
- If Going Downhill – Use the electric trailer brakes to reduce the speed of the caravan, rather than trying to pull up the caravan with the tow vehicle.
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