Are Shackles Necessary For A Single Axle Utility Trailer?

Question:

Are shackles necessary for a utility trailer? I resently restored an older single axle trailer with new leaf springs and axle. I did install shackles but they completely flatten to the frame with my own weight as I jump on the trailer.

asked by: Greg

Expert Reply:

Hello Greg. Generally, yes, shackles are required for any single axle utility trailer. The diagram below will show you the components of a typical single axle setup. You will have shackles on the rear hangers only. This is because as your axle hits bumps in the road it not only gets pushed up, but also back. With the shackle in the back you will have the best ride quality and suspension travel. Without shackles the suspension would likely be quite rough.

The shackles should not be flattening out like that though. This makes me wonder if perhaps the new springs are too long, or the shackles are not the correct size. When you replaced these components, did you make sure the new parts were identical in size to the stock parts? If the parts are not sized correctly, it can throw off the suspension and cause the kind of issue you are describing. The trailer being out of level, or the springs being overloaded could also cause this kind of issue, although it doesn't sound like overloading is the issue.

expert reply by: Jesse M

Single Axle Trailer Suspension Components
(click to enlarge)

Sean

7/3/2024

Hey Jesse, My utility trailer (former double with snowmobile trailer) doesn’t have shackles. It was like that when I bought it used. Based on your comments above, I assume you’d recommend I add them? Thanks, S

Jesse M.

7/3/2024

@Sean How is the ride quality? There are trailers out there that don't use shackles, but the standard for single axle suspension is to use shackles on the rear hanger. The shackles allow the suspension to articulate the way it was intended. If you are unhappy with the current ride quality, then yes, I do recommend that you add them.

John V.

4/30/2025

@Sean wit out the shackles the spring is no different than a solid steel bar the sprinflattens out as it absorbs the bumps in the road and as it does it makes the spring longer if mounted solid it can't flatten out and lengthen so it just acts as a solid mount.