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Replacing noisy Harbor Freight Slipper Springs


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jscherb

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#1
My least favorite feature of the Harbor Freight trailer frames are the "slipper" springs. Slipper springs have only one bolt attaching them to the frame, and the other side of the spring "slips" between the frame and a retaining bolt. They almost always rattle between the frame and the bolt as the trailer goes over bumps. In the illustration below, the left side is from the HF instruction book and shows the stock slipper spring.

The solution to the slipper noise is to replace the springs with shackle-type springs, which are bolted at both ends. There are lots of ways to do this, most involving bolting new spring mounts/shackle mounts to the frame. Places like Tractor Supply sell all the necessary parts and replacement shackle springs. Some people install softer Jeep Wrangler YJ springs with excellent results.

There is also a complete bolt-on solution. Tractor Supply sells 20.25" 1000-lb. capacity shackle-type springs, and these, along with a set of Tractor Supply shackle straps and a few new bolts will bolt right up to the stock HF spring mounts with no drilling or other modifications. Since the HF spring mount is about 2 1/8" wide, and the TSC spring is 1 5/8" wide, a few washers will be needed on the bolt on the spring end of the shackle straps to take up the extra space. The right side of the drawing below shows the shackle spring implementation.

[Image: HFShackleSprings_zps17674a3b.jpg]

Southerncomfort

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#2
I like this idea. May need to look into it.

armyRN

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#3
Especially on the little 4' Harbor Freight type trailers, the factory slipper springs are very stiff. I took a similar approach as Jeff, but I went with 26" long springs (rated 575lbs each) from Stengelbros and bolted them to my trailer's frame. Combined that's still greater than half-a-ton. It involved a little bit more measuring and drilling, but was a total bolt-on affair. Here's a post or two from my Little Harbor Freight (type) Trailer Build regarding the spring conversion (and there's more about it in the pages before and after this post, but this shows it mounted up before final painting and in various stages of completion):

http://www.jeepforum.com/forum/f27/mini-...st14696382
http://www.jeepforum.com/forum/f27/mini-...st14711779
http://www.jeepforum.com/forum/f27/mini-...st14939229

http://www.stengelbros.com/UtilitySprings.htm

[Image: Trailersuspensionmountedup1_zpsd16cce90.jpg]

sburggsx

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#4
Do the Tractor Supply springs add any height at all?

jscherb

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#5
(05-16-2013, 01:46 PM) sburggsx Wrote: Do the Tractor Supply springs add any height at all?

I haven't measured the springs to compare height, but I would expect at least a slight increase in height due to the fact that the rear of the springs are supported by shackle straps.

armyRN

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#6
When I had my factory slipper springs, the axle was mounted under the springs. When I installed the longer 26" springs with a shackle set-up, I moved the axle to above the springs. It still gained me an inch in height measured at the center of the fenders.

sbjeeper84

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#7
I don't know if anybody is running the Tractor Supply springs, but do they help soften up the suspension vs. the Harbor Freight slipper springs? Or is it better going with the longer springs like armyrn to help the suspension do it's job a little better? Or would it help to remove one of the leafs from the Tractor Supply springs to lower the spring rate? Just some random thought that I had when I read this. Seems that if someone did this they would also want to soften up the spring rate a little so the trailer is not bouncing all over if packed light along with getting a quieter suspension.
sbjeeper84, proud to be a member of Tventuring since Aug 2013.

Scott

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#8
Good info. The key is, you want the spring rating matched to GVW of your trailer. As a general rule the longer and flatter a spring is, the softer it rides.

On a side note; have a thread with other info on How-to enhance a Harbor Freight frame for use under a DIY Camping Trailer
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

drswyo

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#9
I just put a new axle on my modified HF trailer using the set up suggested by jscherb. There is a potential problem with the spring and shackle using the stock holes for mounting.

The shackle straps sit just forward of vertical, so as the spring compresses and elongates the shackle has to swing down through it's arc toward the ground, past the vertical position, then up and back through the rest of the arc. Hope I'm explaining that clearly, I'm not clever enough to try and illustrate that.

The result is a very steep climb in spring rate right at the beginning of the suspension travel. Coming from a background in rock crawlers, this makes for a very non-compliant ride.

Seems like the easiest fix is to drill a new rear mounting hole a couple inches forward of the stock hole so that the shackles are always pointing to the rear, but not so far that the spring eye can hit the frame under compression.

For now I'm going to wait until I get my box built and loaded to see where the shackles sit with the spring compressed after dialing in the spring rate by removing leafs, then I'll think about re-positioning the upper shackle bolt.

P.S. One of these days I'm going to get it together and post some build pics, but having trouble finding time to finish the trailer, let along post about it.

Scott

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#10
In theory having the shackle point forward initially is not ideal. When I add spring hangers to a frame, I set the distance between the bolt holes at least a 1/2" less than the distance between the bolt holes on the springs.
Scott Chaney - Owner of Compact Camping Concepts
Home of the DIY Explorer Box and Dinoot trailers, also Tent Topped camping

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