What Is A Leaf Spring? (Everything You Need to Know About Trailer Leaf Suspension)

What Is a Leaf Spring? (Everything You Need to Know About Trailer Leaf Suspension)

If you’ve never had to change your leaf springs before, you might be unfamiliar with what they are and how they function on your trailer; you might not even know what one looks like.

Soon you’ll understand how your trailer’s suspension system operates, recognize the different types of leaf springs, know where they’re located on your trailer, and understand why replacing them consistently is crucial to a stress-free towing experience.

In this article:

What is a leaf spring?
Types of leaf springs
What does a leaf spring do?

Leaf Spring with 6 Leaves vs Leaf Spring with 3 Leaves

What Is a Leaf Spring?

The leaf springs we use on trailers now have been around since the early 1800s, around 1804, to be exact. Composed of between one and seven layers of steel (or leaves), these arched strips of metal attach to your trailer’s frame either above or below the axle.

You might not recognize what your springs do for you while they’re in good shape, but you’ll notice the difference in the quality of your ride when they wear down. That’s why trailer leaf springs are a non-negotiable component when you’re towing. Without suspension, your ride will be bouncy, uncomfortable, and dangerous – even more so if your trailer is unloaded. Your trailer's weight capacity will also be cut in half without leaf spring suspension.

Choosing the Right Replacement Leaf Springs

The number of leaves determines the level of support your trailer will receive. If you have a larger trailer, for example, it’s likely that you’ll need more leaves than if you were hauling a smaller one. However, when choosing a spring, remember that it is your axle capacity that will determine which one is right for you. Most trailers come with leaf springs installed, so you can reference the ones you already have as a guide for finding new ones when navigating your options.

Choosing springs with too high of a weight capacity can result in a stiff ride. Moreover, a weight capacity that is too low may not support your load and lead to a damaged trailer, gear, or both.

Your leaf springs will combine their weight capacities to support your trailer, and there will be two leaf springs attached to each axle. This means a single-axle camper will have two springs, while a dual-axle camper will have four. So, if you have four springs and each has a 3,000-lb weight rating, your springs will support a capacity up to 12,000 lbs.

So, when should you replace your leaf springs? The average lifespan of any kind of leaf spring is about 2-3 years, but this estimate can vary depending on how often you use your trailer. To err on the side of caution, it is best to change them out every few years to avoid cracking or completely snapping while you’re on the road. If you’re unsure of the current quality of your trailer’s leaf springs, you can reference our article, 5 Tell-Tale Signs It’s Time to Replace Your Trailer’s Leaf Springs (And What Healthy Leaf Springs Should Look Like for pointers. If you’re ready to purchase new springs, check out our article, How to Accurately Measure Trailer Leaf Springs.

Types of Leaf Springs

There are two types of leaf springs you’ll encounter: double-eye and slipper springs. Double-eye leaf springs are recognizable by their two “eyes,” while slipper springs are distinguished by their one eye and one open “tail” end. There are various “tail” styles including hook ends, open eye ends, flat ends, and radius ends.

Generally, we recommend you replace your leaf springs with the same kind that came installed on your trailer.

Double-Eye Leaf Springs

Double-eye springs will provide a smoother ride than slipper springs, making them a popular choice for towers with a lighter load.

However, double-eye leaf springs are limited in weight capacity (usually maxing out around 3,000 lbs apiece) and are more prone to wear under the stress.

Slipper Leaf Springs

Coming in weight capacities up to 7,500 lbs apiece, slipper leaf springs have fewer moving parts and are usually found on heavier trailers than their double-eye counterparts. (They’re also noisier due to the way the slipper rests between the top plate and bolt.) Most often, the difference between styles depends on the kind the manufacturer prefers. The different kinds of slipper springs are listed below.

Hook-End Slipper Springs

A hook-end leaf spring has the eye at one end and tapered end at the other.

Open-Eye-End Slipper Springs

An open-eye leaf spring will have an eye at one end and a sharply curled tail at the other.

Flat-End Slipper Springs

Flat end slipper springs are as straightforward as they sound: they possess one end with an eye and another with a flat tail end.

Radius-End Slipper Springs

Radius slipper springs have an eye at one end and an arched tail at the other.

Take-Aways

When you're at the beginning of your search, the choices between the kinds of leaf springs can be overwhelming. Now you’re equipped with the knowledge of types of leaf springs, what they do, and which ones are right for you, meaning you’re closer to a smooth ride you can depend on.

No matter the size of your load, your springs will be prepared to support the weight of your cargo and ambitions alike. Here’s to happy hauling!

About Beth B.

When I explain my position at etrailer to the folks back at home, I usually preface with, “Writing is about 15% of my job. The other 85% is research, hands-on product testing, and putting myself in the shoes of our customers (whom we call neighbors).” At etrailer, I have the opportunity to explore the products I write about in person every day, a privilege many writers don’t have. On a Tuesday morning, for instance, you may find me outside of a 5th wheel collecting pictures of its scissor jacks for an article. On Wednesday, I might switch gears to measure leaf springs in our warehouse, while Thursday is when I’ll finally get behind the keyboard (that is, in between driving off-site to film how-to videos with the team). If you have a question, it’s my mission to not only provide you with an answer, but to equip you with the knowledge and resources you need to face real-world challenges like a pro.

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