What Is Trailer Sway? Causes, Dangers & How to Stop It
- Brent
- Apr 17
- 3 min read
Updated: May 14
If you've ever been towing a trailer and felt it start to wag like a dog’s tail behind you, you've experienced trailer sway. It's not just unnerving — it can be downright dangerous. But what causes trailer sway, and more importantly, how can you stop it before it leads to trouble?
Let’s break it down.
What Exactly Is Trailer Sway?
Trailer sway — also known as fishtailing — is when your trailer moves from side to side behind your vehicle, often in an uncontrolled or rhythmic motion. It can start small, but if left unchecked, it can quickly get worse, causing the driver to lose control and putting everyone on the road at risk.
Trailer sway is most commonly triggered by wind gusts, passing large vehicles, improper trailer loading, or going too fast. Once it starts, it can feel like you're fighting the trailer to keep your vehicle in a straight line — not ideal at 60mph on the M5.
Common Causes of Trailer Sway
Incorrect Weight Distribution: One of the biggest culprits. If the trailer's weight is too far to the rear or off-balance, the trailer is more likely to sway.
High Speeds: The faster you go, the more amplified small sways can become.
Strong Winds: Crosswinds or sudden gusts can push the trailer from the side.
Uneven Tyre Pressure: Mismatched or low tyre pressures can affect how the trailer tracks behind the tow vehicle.
Passing Lorries or Coaches: The wind they kick up can cause a sudden side force on your trailer.
How to Prevent Trailer Sway
Good news — trailer sway isn’t inevitable. Here's how to reduce the chances:
Load Correctly: Aim for 60% of the load weight in the front half of the trailer. Keep the centre of gravity low and secure everything down properly.
Check Your Nose Weight: The downward force the trailer puts on your towbar should be within your vehicle's limits (usually around 7–10% of the trailer’s weight).
Use a Sway Control Device: These clever bits of kit help dampen or prevent sway before it starts.
Keep Your Speed Sensible: Stick to towing speed limits and slow down in windy conditions or when overtaking.
Tyre Checks: Ensure both your vehicle and trailer tyres are at the correct pressure and in good condition.
What To Do If Trailer Sway Starts
If you feel the trailer swaying, don’t panic — and whatever you do, don’t slam the brakes. That can make it worse.
Instead:
Hold the steering wheel firmly.
Ease off the accelerator slowly.
Try to keep your vehicle as straight as possible.
Gently apply the trailer brakes if you have a brake controller fitted.
Once everything is back under control, find a safe place to stop and reassess your load and towing setup before continuing.
Why This Matters for Brent Users
At Brent, we’re all about making trailers easy to hire and buy — but we’re also big on safety. Whether you're towing a car trailer, plant trailer, or anything in between, knowing how to prevent and handle trailer sway is essential. It keeps you, your load, and everyone else on the road safe.
Plus, many of the trailers available through Brent come with features that help reduce sway, from low centres of gravity to optional stabilising systems.
Final Thought - Be prepared
Trailer sway is one of those things you might not think about until it happens — but trust us, it's worth being prepared. A well-balanced trailer, sensible driving, and the right gear can make all the difference.
Next time you're gearing up to tow, remember: a steady trailer is a safe trailer.
-Brent
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