Caravan sway is one of the most frightening and deadly events that can happen to a tower on Australian roads. Understanding the causes — and the correct response — could save your life.
Caravan sway is one of the most frightening and deadly events that can happen on Australian roads. It's a leading cause of caravan rollovers — and it can happen in seconds on a highway, sometimes with little warning. Understanding what causes sway, how to dramatically reduce its likelihood, and critically, what to do if it starts, could save your life.
The RVSafe Road Safety Project, which analysed crashes on NSW roads between 2014 and 2018, identified caravan instability and sway as a recurring factor in serious incidents. Many of these accidents occurred on straight roads at highway speeds — not on tight corners or rough tracks.
What Is Caravan Sway?
Sway (sometimes called "caravan snake" or "fishtailing") is when your caravan begins to oscillate from side to side behind your tow vehicle. Once it starts, it tends to amplify — each swing getting wider — and if not corrected quickly, the caravan can overturn, pulling the tow vehicle with it.
There are two types:
Low-speed sway — typically occurs at parking lot speeds, usually caused by a sharp turn or poor coupling setup. Generally manageable.
High-speed sway — occurs at highway speeds and is the dangerous kind. Can begin as a subtle wobble and escalate to a rollover within seconds if the driver reacts incorrectly.
What Causes High-Speed Sway?
1. Insufficient Tow Ball Download
The most common cause. If not enough weight is pressing down on the tow ball (less than 8% of the caravan's loaded weight), the trailer can "float" and begin to oscillate. This is why weight distribution inside the caravan matters enormously.
2. Exceeding the 85% Rule
When the loaded caravan weighs more than 85% of the tow vehicle's kerb weight, the caravan begins to have more influence on the movement of the combination. Heavy caravans can effectively "wag the dog."
3. Speed
Sway has a threshold speed — below it, the combination is stable; above it, instability becomes possible. This threshold varies depending on the setup, but most combinations become increasingly vulnerable above 100 km/h.
4. Being Overtaken by Large Vehicles
When a large truck or bus passes you at speed, the turbulence can trigger or amplify sway. The pressure wave pushes the caravan sideways, and if conditions are marginal, this can initiate an oscillation cycle.
5. Crosswinds
Strong crosswinds — particularly on exposed highways, bridges, and in cuttings — can push the side of the caravan and initiate sway. High-profile caravans are particularly vulnerable.
6. Sudden Lane Changes or Evasive Manoeuvres
Any sharp steering input that pushes the rear of the caravan sideways can initiate sway if the setup is marginal.
7. Tyre Failure
A blowout — particularly on the caravan — can instantly destabilise the combination. This is why tyre condition and age matters so much on a caravan (many rollovers involve tyres over 7 years old).
How to Prevent Sway
Prevention is far more effective than correction.
1. Get the tow ball download right. Aim for 8–12% of your loaded ATM. Load heavy items forward of the axle and low to the floor. Weigh your rig to confirm.
2. Use a weight distribution hitch (WDH) if appropriate. For heavy setups, a WDH transfers some of the tow ball download to the front axle of the tow vehicle, reducing the "nose up" effect and improving stability.
3. Fit an electronic stability control (ESC) system. Aftermarket caravan ESC systems (such as the AL-KO ESC, Hitch-Pro, or Dexter Sway Control) detect the onset of sway and apply the caravan brakes independently to counteract it. These systems are highly effective and can prevent sway from developing into a rollover. They're worth considering for any caravan regularly towed at highway speeds.
4. Don't exceed your vehicle's rated towing capacity. Your vehicle's towing limit isn't arbitrary — it's the point at which handling and braking are designed to work safely.
5. Observe the 85% rule. Keep your loaded caravan below 85% of your vehicle's kerb weight where possible.
6. Reduce speed in risky conditions. Crosswinds, passing trucks, open exposed roads — drop 10–15 km/h in these situations as a precaution.
7. Maintain your tyres. Check caravan tyre age (not just tread depth — sidewalls degrade with UV exposure). Replace tyres over 7 years old regardless of how they look.
What to Do If Sway Starts
This is where most people get it dangerously wrong. The instinct is to brake hard or steer to correct — both of which can make sway catastrophically worse.
The correct response to caravan sway:
- Do NOT brake suddenly — unless you have a caravan ESC system, hard braking can amplify sway
- Do NOT steer to correct — counter-steering can increase the amplitude of the oscillation
- Ease off the accelerator smoothly — reducing speed is the most important action
- Hold the steering wheel firmly and straight — resist the urge to steer
- Allow the combination to slow down naturally — as speed reduces, sway will reduce
- Apply a light, steady brake — once speed has dropped, gentle braking helps stabilise
- Pull over safely once sway has stopped — do not continue until you've identified the cause
If your vehicle is fitted with a modern ESC system and your caravan has an aftermarket sway controller, these systems will apply independent braking to the caravan automatically — your job is to keep the steering wheel steady and ease off the throttle.
After a Sway Event
Even if you've recovered safely, don't just drive on. Stop at the next safe location and:
- Check your tow ball download — something in the caravan may have shifted
- Check tyre pressures on both vehicle and caravan
- Check coupling and safety chains
- Check caravan contents — heavy items may have moved during the oscillation
Understanding sway and preparing for it is central to what the RVSafe project teaches. Their free guides and videos are worth reviewing before your next trip.
Further reading: RVSafe Towing Safety Guide | Browse caravans with compliance data on Camplify Xchange
Part of the Camplify Xchange editorial team, sharing expert RV advice for Australian adventurers.
