How to Determine Which is Correct Replacement Leaf Spring

Question:

Im trying to find the correct leaf springs for my trailer. What is the best way to find that?

asked by: Matt L

Expert Reply:

You'll need to determine three things in order to determine what the correct replacement leaf spring you need for your trailer.

• Is it a Double Eye or a Slipper Spring?
• What's the Length of the Spring?
• What's the axle capacity?

I've provided a photo showing what a typical double eye and a slipper spring look like. The big difference between the two is a slipper spring will only have a spring eye on one end.

The diagrams in the photo will also show you how to measure your existing springs. To get an accurate measurement, you'll need to take your measurement with the trailer up on jack stands so the suspension hangs free because leaf springs will flatten out over time as they wear.

The axle capacity is a little trickier to determine. Many times, there's an axle tag that will provide its capacity. If that's not present, finding the reference numbers from the inner and outer wheel bearing and the wheel bolt pattern (see linked help article which shows how to measure for bolt pattern) will help us make a highly educated guess as to the axle capacity. For instance, an axle rated for below 2000 lbs will typically use a straight spindle with an L44643 inner and outer wheel bearing. The bolt pattern would be a 4 on 4.

For axles between 2000-3500 lbs, a straight spindle would also be used with an L44649 inner and outer bearing and either a 4 on 4 or a 5 on 4-1/2 inch bolt pattern.

A 3500 lb axle is very common and would have a tapered spindle that uses an L68149 and a L44649 outer bearing. The bolt pattern is almost always a 5 on 4-1/2.

In many cases, the diameter of the axle tube can also be a clue as to the axle capacity.

• If the axle is 1 to 1-1/2 inches in diameter-it's likely a 1000 lb axle
• 2-3/8 in diameter-3500 lb axle
• 3 inches in diameter, 6000-7200 lb axle
• 3-1/2 inches-8000 lb axle
• 4 inches-9000 axle
• 5 or more-10000 lb axle

If you can compile as much of this information as possible, we can help find the correct leaf springs for your needs. I'll also link to a couple of help articles that will provide additional information about double eye and slipper spring suspensions.