How to Select the Correct Leaf Spring Size for a Tandem Axle Trailer with Slipper Springs

Question:

I have a duel axle trailer with 4 leaf Slipper springs. They are 1 3/4inch wide and from bolt to bolt it is 26. The springs are out of shape so I cant get a good overall length. What size would fit?

asked by: Larry D

Expert Reply:

To determine the correct slipper springs for your tandem axle trailer, the axle capacity will need to be determined. Selecting a spring by length alone could cause the selection to be under or over capacity substantially.

If your spring is shaped like the 4-Leaf Slipper Spring for 4,100-lb Trailer Axles, # e33SR, and each axle capacity is 4,100 lbs or just below that, then this spring should work for you. This is the only spring we have with the slipper end shaped this way.

If your slipper springs are a more standard design, like part # SP-040275, the axle capacity is going to determine which of several different springs could be used for your trailer. The number of leaves is not a good indication of spring capacity because trailer springs are rated for carrying capacity and the number of leaves in the spring can change to create a spring of the correct capacity.

If the number of leaves in the spring pack change and considerably thicker or thinner springs are used, U-Bolt dimensions may have to change so that they can be correctly installed. Your axle diameter and spring width, 1-3/4 inches in this case, will also be needed to select the correct U-Bolt kit. I added a link to our U-Bolt kits for you to select from.

Since your springs are out of shape, they may have flattened and elongated due to wear and age. Typically about 1 inch of elongation is all you see on trailer springs so you may need a spring in the 25 to 26 inch range. You can also check the spring half length which would show much less elongation and may help determine the correct spring for your trailer. See attached photo for where to measure. If you would like to send me some more information and photos, I will be glad to help you select the correct springs for your trailer.

expert reply by: Robert G