Symmetric vs. Asymmetric Sway Control: What’s the Difference?

If you tow trailers, caravans, or horse floats, you’ve probably heard the expression “the tail is wagging the dog.” It’s a fun saying, but also a surprisingly accurate description of what happens during a sway incident: swaying trailers are strong enough to pull the towing vehicle out of control. Swaying trailers are a major hazard on Australian roads and cause thousands of accidents every year; in fact, trailer sway is attributed as the cause of 91% of caravan accidents in Australia.

That’s why sway control systems are a crucial addition to any towing set-up: counteracting the danger of out-of-control caravans and horse floats to prevent road accidents.  

However, the choice between symmetric and asymmetric sway control systems can be confusing – a choice made even more difficult knowing just how critical the right sway control system is to road safety. As the experts, Tuson is here to explain the differences between symmetric and asymmetric sway control to help you make an informed decision for your caravan or horse float towing setup.

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What Causes Trailer Sway?

Yaw, snaking, swing, fish-tailing, tow wobble – whatever you call it, trailer sway is a major danger when towing caravans and horse floats. Trailer sway is caused by simple physics: as Newton’s First Law of Motion states, a body in motion remains in motion unless acted upon by an external force. Trailer sway is caused by external forces creating momentum on the trailer that pulls the towing vehicle out of control.

These external forces can be caused by elements such as:

• strong winds, bad weather
• low-pressure shakes from passing cars
• high speeds
• poor road conditions
• oversteering
• unbalanced or underinflated tyres
• off-centre or overloaded tow loads
• uneven hitching

There’s a long list of hazards that can cause your horse float or caravan to sway out of control, but trailer sway can occur seemingly out of nowhere, even on good roads and in good weather conditions.

Like Newton said, once a body is in motion it will stay in motion – which is why when a trailer starts to sway, unless acted upon, it will continue to swerve and pull from side to side in increasingly wider arcs from the ‘fulcrum’ of the towing hitch point.

This is why sway control systems are so critical for your caravan or horse float: to mitigate the sway caused by these external forces, the force needs to be counteracted. Sway control systems essentially balance out the swing of the swaying trailer by apply a “stopping force” of brakes.

Both symmetric and asymmetric sway control systems counteract sway by applying brakes, but they do this using different braking methods – some safer than others.

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Symmetric Sway Control:

Symmetric sway controllers activate all trailer brakes simultaneously when detecting a sway event to reduce the tow vehicle and trailer speed. This is labelled ‘symmetric’ sway control because the brakes are applied at the same time on both sides, mimicking the action of manually applying trailer brakes to slow down. The symmetric sway control method may effectively reduce towing swing, but lacks the precision and versatility of asymmetric sway control. While slowing the tow vehicle, symmetric sway control does little to offset the force and momentum causing your caravan or horse float to sway. While it reacts quickly to initiate braking, symmetric sway control lacks the ability to provide varying left and right side forces, ultimately making it less effective in reducing trailer sway.

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Asymmetric Sway Control:

Unlike symmetric sway control, asymmetric sway control independently applies the left or right brakes – not both brakes. Applying the brakes on one side generates enough force to counteract sway. For instance, if a wind gust pushes the trailer to the left, the application of left brakes pulls the trailer back to the right, offsetting the sway momentum. Asymmetric sway systems adjust brake pressures based on sway velocity, acceleration, and angle, effectively reducing sway without compromising vehicle speed. Asymmetric sway control is a delicate balance and requires mathematical precision to correct sway without pulling the out-of-control tow load too far in the opposite direction and cause an even larger incident: that’s where Tuson can help.

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Why Tuson Asymmetric Sway Control:

The most intelligent electronic sway control system on the market, Tuson Asymmetric Sway Control system minimises the complex mathematical equations and physics, providing varying levels of side forces on a trailer. Unlike symmetric systems, asymmetric sway controllers independently apply the left and/or right brakes at different levels during a sway event, countering side forces more effectively.

When Tuson’s Sway Control detects trailer sway, it applies the brakes asymmetrically to directly counteract the sway velocity and aggressively control it without having to rely on speed reduction. The brake application transitions from side to side until the trailer sway is brought under control. By constantly monitoring for sway, Tuson’s Sway Control can instantly detect and counteract swaying trailers before they swing out of control. In the time it takes to blink, Tuson Sway Control can automatically and instantly correct the sway on your trailer two hundred times – an electronic solution that mitigates sway risks often before the driver even realises there’s an issue.   

During a sway emergency, the tow vehicle experiences forces at multiple pivot points, including the hitch ball and the trailer axles where tyre contact with the road occurs. Tuson Asymmetric Sway Control, through its instant brake application, pulls back on the ball hitch at the exact velocity to align the trailer with the tow vehicle and reduce sway angles. This process is automatically adjusted based on factors like tow vehicle weight, trailer tyre traction, and brake conditions – showcasing why Tuson Sway Control is the smartest system in the market and the right choice for safeguarding your caravanning and horse float travels.

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Asymmetric sway controllers, exemplified by Tuson’s technology, are the superior choice for effectively reducing trailer sway. By independently applying brakes at varying levels and accounting for factors like tow weight and speed, the Tuson asymmetric sway systems provide precise and dynamic control, ensuring a safer and more stable towing experience on your next journey. Contact the Tuson team to tow with peace of mind: