How to Measure Trailer Leaf Springs
Jul . 17, 2025 10:08
When it comes to replacing your trailer leaf spring, one of the most crucial steps is making sure you take the correct measurements. Whether you're upgrading a worn-out spring or simply replacing a damaged one, knowing how to measure trailer leaf springs properly can save you time, money, and a lot of frustration. In this guide, we'll walk you through the step-by-step process, explain common mistakes to avoid, and help you choose the right part for your trailer.
Why Measuring Your Trailer Leaf Spring Matters
Leaf springs are essential to the suspension system of your trailer. They support the weight of the load, absorb road shock, and maintain proper tire alignment. However, over time, they wear down due to repeated stress, corrosion, or heavy loads. This can lead to sagging, cracking, or even total failure. That’s why timely replacement with the correct size and type of trailer spring is critical.
If you purchase a spring that’s even slightly too short or too long, it won’t fit correctly, and could compromise the safety of your trailer. That’s why learning how to measure trailer leaf springs correctly is a key skill for trailer owners and fleet operators alike.
Tools You’ll Need
Before you begin, gather the following tools:
Tape measure (preferably a flexible one)
Pencil and notepad or phone for recording measurements
Jack and jack stands (if removing the spring)
Camera (optional, to capture visual references)
Step-by-Step: How to Measure Trailer Leaf Springs
1. Identify the Type of Leaf Spring
There are different types of trailer springs, including:
Double-eye springs (with round eyes on both ends)
Slipper springs (with one eye on one end and an open or hook-shaped end on the other)
It’s important to know which one your trailer uses, as the measurement process differs slightly between types.
2. Measure the Eye-to-Eye Length
For double-eye springs, measure the distance from the center of one eye to the center of the other. This is called the “eye-to-eye length.” Make sure the spring is not under load when measuring—it should be removed or the trailer should be jacked up.
For slipper springs, measure from the center of the eye to the end of the slipper (the furthest tip of the open end). This is called the “eye-to-end” measurement.
3. Measure the Width of the Spring
Use your tape measure to check the width of the leaf spring across its arch. The most common widths for trailer springs are 1.75 inches and 2 inches. Measuring the width accurately is essential because spring hangers and mounting hardware are designed for specific widths.
4. Count the Number of Leaves
Leaf springs can have anywhere from one to several “leaves” or metal strips stacked together. Count the number of leaves in the spring, as this affects the spring’s load rating and compatibility. More leaves generally mean more strength and a higher load capacity.
5. Determine the Arch (Free Arch Height)
Lay the spring flat on the ground, and measure the vertical distance from the center bolt (the tallest point of the spring) down to the floor. This is called the free arch height and tells you how much curve the spring has when unloaded. A worn spring will often have a flattened or reversed arch.
6. Take Note of Bolt Hole Size
Most trailer leaf springs attach using bolts that fit into the eyes. Make sure to measure the diameter of the bolt hole in the eye to ensure the new spring will fit your hardware. Common sizes are 9/16", 1/2", and 3/4", but it’s best not to assume—always measure.
Bonus Tip: Compare to Leaf Spring Manufacturer Specs
If you have access to the original equipment manufacturer (OEM) specifications for your trailer model, compare your measurements to those specs. This can help confirm that you’ve taken the right measurements and help you choose a direct-fit replacement.
Mistakes to Avoid When Measuring Trailer Leaf Springs
Measuring under load: Always remove the spring or unload the trailer before measuring to avoid incorrect dimensions.
Ignoring spring fatigue: Don’t measure a worn-out spring and assume it reflects the original size. Look for signs of sagging or reverse arch.
Forgetting bushing sizes: Some replacement springs come with bushings pre-installed. Check that the inner diameter matches your existing bolts.
Mixing spring types: Don’t assume that all springs are interchangeable. Double-eye and slipper springs are mounted differently and require specific brackets.
Final Thoughts: Measure with Confidence, Replace with Precision
Knowing how to measure trailer leaf springs ensures that you get the correct replacement part that fits your trailer and performs reliably. Taking time to measure properly saves money, prevents downtime, and most importantly, keeps your trailer safe on the road. Whether you're dealing with light-duty utility trailers or heavy-duty cargo haulers, investing in the right leaf spring is a smart decision.
At Hebei Minmetals, we offer a wide selection of trailer leaf springs to suit various models, load ratings, and mounting systems. All our springs are manufactured to high-quality standards, using treated alloy steel for strength and longevity. Need help confirming your measurements? Our support team is ready to assist you every step of the way.
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