Axle springs mounted on top or bottom, which is better?

[bitternut]

I have a 7x12 12,000# dump trailer with the springs mounted on the bottom which results in minimum clearance between the fender and the tire. I have noticed some other dump trailers have a very large amount of clearance and the springs are mounted on the top. What are the pros and cons of each method?

 

[4570Man]

Usually the lower to the ground you can get without rubbing the wheels the better. But with a dump trailer more height would be an advantage while dumping. The lower to the ground the farther it’s going to spread the pile.

 

[Renze]

Its whatever ride height you need. And off course the drawbar height should match your tow vehicle.

With small commercial trailers we used underslung for deck-over stepframe equipment trailers, and overslung for flatbed cargo trailers. These were the same components, just different in assembly..

 

[BrkMstr]

Strickly clearance choice, I like the deck over for the height, to me it's easier to dump, don't have to worry about bottoming. I don't have any issues in loading my tractor, but for some the under works better for loading equipment, and if they have a smaller tractor they are easier to load - again mostly choice......

 

[Hay Dude]

Springs on top, more tippy, steeper load angle if loading wheeled/tracked equipment on ramps

 

[bitternut]

Well since the trailer is used as only a dump trailer the extra height would be a plus when dumping material. When dumping now I have to move ahead a few times which spreads the length of the pile. At present, there is only about an inch or so clearance between the top of the fender and the tires. The springs are still arched but they could have flattened some from the original arc I suppose. I have noticed scuff marks from the tire tops contacting the fenders a couple of times when heavily loaded. Hauling stone from the quarry is when I have noticed the tire rub marks when I was overloaded. Seems as though if you want 5 ton of stone you better ask for 4 ton. I came off the scale once with a little over 7 tons of stone. That was a slow ride home. Got lucky when it was time to dump the load. Yea it dumped it OK. Thought all the way home that I was going to have to shovel some off.

Anyway, I think I will consider getting a kit to change the trailer axles to overslung from underslung. The trailer is about 8 years old so most likely the shackles and bushings might be ready for replacement. The trailer is never driven on salted roads so I have plenty of time waiting for spring's arrival. Might as well make good use of the off-season to complete the project.

Searching further I found some detailed info on flipping the axles and even found detailed instructions. Here are the links if anyone is interested. I will report back on the results when completed.
How To Flip Axles On A Trailer For Better Boondocking.

Overslung or Underslung Trailer Springs? – Mechanical Elements