How to Stop Trailer Sway – What it is and how to avoid it

If you’ve ever towed a trailer, you know that unsettling side-to-side motion that makes your vehicle feel harder to control. This is called trailer sway, and it’s a serious safety concern that every trailer owner should understand. What may start as a minor wobble can quickly escalate into a very dangerous situation. However, trailer sway can be prevented. By focusing on weight distribution, tongue weight, speed, and proper equipment, you can tow safely and keep your trailer tracking straight.

In this guide, we’ll explain what causes trailer sway, how to prevent it, and what to do if it happens while you’re on the road.

What Is Trailer Sway?

Trailer sway is the side-to-side movement of a trailer that occurs when it doesn’t follow directly behind your tow vehicle. A small amount of sway is normal, especially above 45 mph, but it becomes dangerous when it reacts too much to steering and starts to fishtail. Persistent or severe sway signals that your setup needs adjustment.

Unchecked trailer sway can cause:

• Fishtailing: The trailer swings wider and wider, pulling your vehicle with it.
• Jackknifing: The trailer swings sharply against the tow vehicle, often during skids. This is most common with larger trucks and trailers.
• Vehicle and trailer damage: Heavy sway stresses your suspension and hitch, and in extreme cases, can even flip the trailer.

What Causes Trailer Sway?

Trailer sway happens when the balance between your tow vehicle and trailer is disrupted. Common causes include uneven loading, crosswinds, or a difference in speed between the towing vehicle and the trailer. Once the trailer begins to sway, each movement compounds the imbalance, making it increasingly difficult to control.

Factors that make sway more likely or severe include:

• Uneven, unbalanced or overweight loads: Rear-heavy trailers are harder to control. If the center of mass is behind the rear axle, lateral shifts will have greater force.
• Long and/or tall trailers: They catch more wind, increasing lateral motion.
• Incorrect tongue weight: Too much or too little weight on the hitch decreases stability.
• High speeds: Faster driving amplifies sway.
• Passing large vehicles: The wind from other vehicles can trigger unexpected sway.
• Strong crosswinds: Side winds push the trailer off track.

While you can’t control everything on the road, you can minimize sway by adjusting your trailer setup and following safe towing practices.

How to Prevent Trailer Sway

A well-prepared trailer setup combined with smart driving habits is the best way to prevent sway. Here are the key strategies:

1. Balance Your Load with Proper Tongue Weight

Tongue weight—the downward force your trailer’s tongue/coupler exerts on the towing vehicle’s hitch—should be 10–15% of the trailer’s total weight.

• Too little tongue weight: Increases reactive sway.
• Too much tongue weight: Overloads your tow vehicle and may exceed its payload.

You can adjust tongue weight by moving heavy items forward (toward the tongue) or back (away from the hitch) to achieve balance. (See our safe loading guidelines for more.)

2. Follow the 60/40 Rule

Distribute 60% of cargo weight in front of the trailer axle and 40% behind. This keeps more weight toward the tow vehicle, reducing sway and improving stability. Some trailers are designed with a rearward axle to make front-loading easier.

3. Use the Right Tires and Maintain Proper Pressure

Even a balanced trailer can sway if the tires aren’t suitable. Increase tire pressure (within safe limits) for a firmer, more stable ride. If the towing vehicle is running passenger rated (p-rated) tires, you should upgrade to LT (Light Truck) or higher-rated tires to handle greater weight and sidewall stress. P-rated tires aren’t designed for towing stability, and LT and higher-rated tires can handle higher pressure and greater sidewall stress.

4. Slow Down in Wind or Poor Conditions

High speeds worsen sway, especially in strong crosswinds or when passing large vehicles. Reduce speed below highway limits when conditions on the road require it (high winds, rain, stop and go traffic, ice, low visibility, etc.). Some trailer manufacturers also recommend certain speed limits for their trailers, so follow those.

5. Match Trailer Length to Your Vehicle’s Wheelbase

A vehicle’s wheelbase limits the safe length of the trailer you can tow. Use this simple formula:

Wheelbase in inches ÷ 5 = maximum trailer length in feet

So an F-250 with a 141-inch wheelbase can safely tow a trailer up to about 28.2 feet long.

6. Use Trailer Sway Control Devices

Sway bars, sway hitches, and built-in vehicle sway control systems help reduce side-to-side motion:

• Sway bars:Installed on one or both sides of the hitch, they stabilize the trailer.
  • Trailers under 10,000 lbs: one sway bar
  • Trailers over 10,000 lbs: two sway bars
• Sway hitches: Hitches with built-in friction or cam systems dampen sway without additional attachments.
• Vehicle sway control: Some vehicles automatically detect sway and adjust braking or engine power, similar to traction control or lane-keeping assist.

What to Do If Your Trailer Starts Swaying

Learn this well so you can remember it in an emergency.

If sway occurs while driving, stay calm. Avoid sudden steering or braking, which can make it worse. You must stop accelerating and slow down the trailer without using the truck’s brakes.

Gently slow the trailer using the trailer’s brakes to regain control.

Steps to regain control:

1. Stop accelerating and remove your foot from the gas.
2. Keep the tow vehicle straight and gently apply the trailer’s electric brakes.
3. Once the trailer is aligned, release the trailer brakes and continue driving.

What Not to Do:

• Do not use the tow vehicle’s brakes to slow down—the trailer will push harder against the hitch.
• Avoid steering side-to-side to correct sway; this usually amplifies the motion.

Smaller trailers are not required to have brakes, depending on state and local laws. What if your trailer is swaying and it doesn’t have brakes?

Steps to Control Trailer Sway Without Trailer Brakes

1. Stay Calm and Don’t Oversteer. Avoid sudden steering corrections. Overreacting can make the sway worse. Keep your hands steady and your vehicle pointed straight.

• Gradually Reduce Speed. Gently lift your foot off the accelerator to slow down. Don’t slam the tow vehicle brakes—this can push the trailer harder, increasing sway.
• Use Engine Braking. Downshift if you’re driving a manual or use your tow vehicle’s engine braking to slow gradually. This reduces speed without creating a strong push from the trailer.
• Increase Distance From Other Vehicles if Possible. Sway can be exacerbated by wind from passing trucks or large vehicles. Give yourself extra space and let them pass safely. But make sure all turns are extremely gradual:
• Steer Straight and Smoothly. Avoid weaving or quick corrections. If you must steer, make very small, smooth adjustments to keep the trailer aligned.

6. Pull Over Safely If Needed. If sway persists and conditions allow, find a safe place to stop.
7. Check your load distribution and make adjustments before continuing.

What if your trailer is large enough that it’s required to have brakes, but they’re not working?

That could be really bad. Don’t put yourself in that position. The steps to try to regain control are the same as above but you’re in a much riskier and more dangerous situation. If you didn’t load the trailer properly and your brakes aren’t working, buddy, whatever happens on that highway is on you now. 

JTI does service trailer brakes though! Give us a shout if you’re not sure about your trailer’s brakes. Call our service department at 440-232-4311.

For more loading tips, see our quick guide to safely loading your trailer!