How Can I Tell If My Trailer Hitch Is Causing My Car to Sag?

How Can I Tell If My Trailer Hitch Is Causing My Car to Sag?

SCOTT MCCUSKEY @ May 20, 2025

Towing a trailer opens up many possibilities—from hauling equipment to taking your camper on a weekend getaway. But what happens when your vehicle starts to sit lower in the back while towing? This visible rear-end dip is often a sign of vehicle sag—and it may be your trailer hitch causing it.

Whether you're new to towing or a seasoned hauler, it's crucial to know how to identify and fix hitch-related sag. Letting it go unchecked can negatively affect safety, handling, and the life of your suspension system.

In this guide, we'll explore what causes sag, how to tell if your trailer hitch is to blame, and how to correct the problem effectively.

What Is Vehicle Sag?

Vehicle sag refers to a noticeable drop in the rear suspension of a car, SUV, or truck. This typically happens when extra weight is applied to the back of the vehicle—like a trailer, cargo carrier, or bike rack mounted to the hitch.

While a small amount of compression in the rear suspension is normal when towing, excessive sag is a sign of overload or imbalance. This can:

• Reduce steering and braking performance
• Cause headlight misalignment
• Increase wear on tires and suspension
• Make your ride uncomfortable or even dangerous

Why Trailer Hitches Can Cause Sag

To understand how a hitch can cause sag, we need to talk about tongue weight.

Tongue weight is the downward force the trailer exerts on the hitch. Most trailers put 10–15% of their total weight on the hitch. So, a 3,000-pound trailer may exert 300–450 pounds of tongue weight on the rear suspension.

If the tongue weight is too heavy—or if it's improperly balanced—it can overload the rear suspension and cause noticeable sag. Even a hitch-mounted cargo carrier or bike rack can cause sag if it exceeds the vehicle’s load capacity.

Common Signs That Your Hitch Is Causing Sag

1. Rear End of the Vehicle Is Visibly Lower

This is the most obvious indicator. If you notice that your car or truck looks like it's "squatting" in the back—especially when the trailer is hitched—it’s likely experiencing sag.

You can measure this by:

• Taking a pre-tow measurement from the ground to the top of the rear wheel well
• Comparing it to the hitched measurement with the trailer or load attached

A difference of more than 1.5 to 2 inches usually indicates significant sag.

2. Front End Lifts Up

When the rear end sags, the front end may lift slightly. This negatively affects steering traction, braking efficiency, and headlight aim—making night driving more dangerous.

3. Braking Feels Sluggish or Unstable

If the front end is too light due to rear sag, the front brakes don’t engage as effectively, and stopping distances increase. You might also notice the vehicle swaying or dipping during braking.

4. Rough or Bumpy Ride

A sagging rear suspension might bottom out over bumps. If you feel the vehicle hitting its bump stops or notice a rough ride while towing, it's a sign the suspension is overloaded.

5. Excessive Wear on Rear Tires or Suspension

Long-term towing with a sagging hitch can lead to:

• Uneven or accelerated rear tire wear
• Premature shock and strut failure
• Increased strain on leaf springs or coil springs

Inspect your rear tires and suspension components regularly if you tow often.

Diagnosing the Cause: Is It the Hitch, Load, or Suspension?

If your vehicle sags when towing, you’ll want to determine whether the issue is:

1. An overloaded or improperly used hitch
2. Excessive trailer tongue weight
3. Worn or inadequate suspension components

Step 1: Verify Your Vehicle’s Towing and Tongue Weight Capacity

Check your vehicle’s owner’s manual for:

• Maximum towing capacity
• Maximum tongue weight
• Maximum payload

Compare this to the actual trailer weight and tongue weight. You can measure tongue weight using:

• A tongue weight scale (available at RV or auto stores)
• A bathroom scale trick (for lighter trailers)
• Professional weigh stations

If the tongue weight exceeds your vehicle’s rated capacity, that’s likely the cause of sag.

Step 2: Assess Load Distribution in the Trailer

Improperly distributed trailer weight can increase tongue weight. For safe towing:

• Keep 60% of the trailer's weight in front of the axle
• Ensure the tongue weight is 10–15% of the total trailer weight
• Avoid loading too much toward the front

Use a weight distribution system if necessary (more on this later).

Step 3: Inspect Suspension Components

Older vehicles or frequently used tow vehicles may have worn:

• Coil springs
• Leaf springs
• Shocks or struts

Worn suspension can cause sag—even with a properly loaded trailer. Look for:

• Leaking or weak shocks
• Cracked or broken springs
• Excessive bounce when pushing down on the bumper

If your vehicle sags even when unloaded, it may be time for suspension repair.

Solutions to Fix or Prevent Hitch-Related Sag

Fortunately, there are several ways to fix or prevent trailer hitch sag, depending on the cause.

1. Redistribute the Load

Before upgrading parts or spending money, check your trailer’s load distribution. Move heavy items closer to the trailer’s center or axle. This often reduces tongue weight and minimizes sag.

2. Use a Weight Distribution Hitch

A weight distribution hitch (WDH) is a great solution for trailers over 3,000 pounds or those with heavy tongue weights.

A WDH:

• Distributes weight evenly across all axles of the tow vehicle and trailer
• Reduces rear sag and front lift
• Improves braking and steering
• Creates a safer and more level ride

Make sure your trailer and hitch are compatible with a WDH, and follow installation guidelines carefully.

3. Upgrade Your Suspension

If you frequently tow heavy loads, consider enhancing your vehicle's suspension:

• Air helper springs: Adjustable air bags that support extra weight
• Heavy-duty shocks: Improve ride stability under load
• Load-leveling systems: Automatically adjust suspension height
• Add-a-leaf kits: Increase the load capacity of leaf spring setups

These upgrades can dramatically improve towing performance and reduce sag.

4. Install a Hitch Cargo Carrier with Caution

Even hitch-mounted carriers or bike racks can cause sag if overloaded. Always:

• Check your vehicle’s tongue weight rating
• Avoid exceeding the hitch’s maximum tongue load
• Distribute weight evenly on the carrier

If you’re close to capacity, consider a roof cargo box instead.

5. Routine Maintenance and Monitoring

Stay ahead of problems by:

• Checking tire pressure and condition
• Inspecting suspension before long trips
• Weighing your loaded trailer periodically
• Watching for signs of unusual wear or alignment issues

Prevention is always better—and cheaper—than repairs.

When Is Sag a Serious Problem?

A little suspension dip is normal when towing, but if you notice any of the following, it’s time to act:

• More than 2 inches of sag in the rear wheel wells
• Front-end lift causing visibility or handling issues
• Bottoming out or bouncing excessively
• Trailer sway or instability at highway speeds

Ignoring these issues can lead to dangerous driving conditions, especially when braking or cornering.

Summary: Key Takeaways

Final Thoughts

Towing safely isn’t just about hooking up a trailer and hitting the road—it requires balance, awareness, and the right equipment. If your trailer hitch is causing your car to sag, don’t ignore the signs. Whether it’s a small dip or a big problem, identifying and correcting sag will make your towing experience smoother, safer, and easier on your vehicle.

Start by checking your tongue weight and trailer loading, then evaluate whether your vehicle’s suspension is up to the task. With the right approach—be it load redistribution, a weight distribution hitch, or a suspension upgrade—you can tow with confidence, knowing your setup is stable and safe.