Why is my trailer swaying? Common causes and how to prevent it

Experiencing a swaying trailer during a high-speed haul can be every truck driver’s worst inconvenience. While experienced drivers certainly have the skills
to handle the situation, trailer sway can happen very quickly which can take even the most seasoned professionals off-guard.

It is vital for truck drivers to be equipped with the skills to be able to make it out of unexpected trailer sway safely. Equally important is to be aware of
the contributing factors which cause trailer sway in order to be able to avoid it.

If not handled correctly, trailer sway or “fishtailing” can be problematic. Here is a list of common causes of trailer sway and tips for how to prevent it
from occurring altogether.

Common causes of trailer sway
 

The most common cause of trailer sway is exposure to strong crosswinds which hit from the side and force the momentum of the trailer to divert
direction from side to side.

Semi-trailers that attach to a truck’s fifth wheel commonly don’t experience many effects of crosswinds as they are firmly harnessed into the weight
distribution of the truck. Full trailers, on the other hand, do experience sway from strong winds largely because they do not generate their own
forward momentum which creates a force that can mostly withstand crosswinds.

Trucks pulling full trailers or combination train configurations connected by drawbar pintle/hook attachments are the most vulnerable to sway from
strong gusts of wind.

Another common cause for trailer sway is a different form of wind force. Large passing trucks can sometimes create a fierce tailwind that ejects a
strong gust force to the rear and sides of a pulled trailer.

Apart from wind force, other factors which are known to contribute to trailer sway are uneven road infrastructure and potholes.

How to prevent trailer sway
 

• Truck and trailer maintenance

The most crucial step to safeguard your trailer from experiencing sway is to ensure that your mechanics are functioning optimally at all times.
Regularly inspecting and servicing your truck and trailer will ensure all hardware is doing what it is supposed to and providing reliability at all times.

Consistently checking that all vales, bolts, and connections are tight and greased and that all electronics and mechanics are functioning will
give you peace of mind that your hardware won’t let you down during a haul. Ensuring your trailers and trucks are at optimal functionality
reduces risk when faced with trailer sway.

• Weight distribution

Understanding the importance of weight distribution is a crucial piece of knowledge all drivers must understand. When a trailer’s goods are
loaded unevenly, it creates a weight imbalance which will amplify when wind or a sharp turn alters the momentum from straight to side to side,
causing sway and danger for all road users.

Drivers must make sure that trailers are loaded with the correct weight and that the goods are placed in specific ways to ensure proper weight
distribution. Loading more weight in the front of the trailer and placing goods evenly on the left and right will help maintain the correct weight
balance – which is crucial to avoid trailer sway.

Trailers with pintle hooks should have a tongue weight of roughly 10% of the total trailer weight to help reduce the potential for oversteering.

• Load capacity

Overloaded trailers can be volatile on the roads. With all their experience, professional drivers may not able to handle an overloaded and swaying
trailer as the force is too great. Every trailer has a maximum weight that it is able to safely handle – anything above this weight increases
the risk of sway.

Drivers need to be aware of the overall trailer weight, including trailer payload and tongue weight limits. Inspecting the tow ratings for each
component will ensure loads never go over the trailer’s weight limit.

• Truck type

Every truck is best suited to particular needs and requirements. The capabilities of a truck will determine the type of trailer and weight
capacity it is able to handle. To avoid trailer sway, you need to use a truck that is heavy and long to provide enough stability and power
to generate forward momentum that reduced the risk of sway from crosswinds.

Trucks with a long wheelbase provide more stability to withstand the effects of sway as more surface area on the ground creates increased
stability. The greater the distance between a truck’s wheels the better it is able to counteract trailer sway.

Additionally, trucks and trailers with rear dual wheels handle trailer sway better because of the added traction provided by the extra wheels.

• Cautious driving

Defensive and cautious driving is the cornerstone of safe overland logistics and must be adhered to at all times to ensure the safety of road
users. Drivers must be aware that any sudden movements such as slamming on brakes or overcorrection of steering will increase the risk of
trailer sway. Even if a trailer’s load distribution and load capacity are correct, abrupt movements and changes will alter the trailer’s
momentum and create shifts in balance.

Drivers must always create a safe distance between themselves and the vehicles in front, behind, and next to them to provide more reaction
time. Pre-planning trips will help drivers to anticipate routes, making lane changes and turns more predictable. This helps to avoid any
sudden surprises which require evasion techniques that can lead to trailer sway.

Summary
 

While trailer sway is a common occurrence in overland logistics, there are a few actions you can take to reduce the risk when it happens. Drivers
need to be aware of the contributing factors which cause trailer sway in order to be able to safeguard against it.

If you maintain your truck and trailer to ensure all parts are working as they should, distribute the goods evenly without overloading, use the proper truck,
and drive cautiously, you will be able to reduce the risk of fishtailing tremendously.