Trailer axle, above the spring or below the spring, does it matter?


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Old 04-16-10, 04:06 PM
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Trailer axle, above the spring or below the spring, does it matter?

My last trailer came both ways, some had the axle below the axle and some had it above. I prefer the axle below the spring to get the extra few inches of height. The new trailer that I am looking at comes with the axle above the spring and I think that I want to change it.

Is there any reason not to move it other than the fact that I realize that the axle has a predetermined bow, obviously I have to keep it with the bow up. I may have to cut off the spring perches and reweld them on the bottom, and there may be a modification with the center bolt.
 
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Old 04-16-10, 05:02 PM
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If it's a new trailer your looking at, get the builder to change it before you buy it.. If you modify it after you buy it & it doesen't tow well,, you have no recourse... Most trailer builders I have talked to will build to spec... Check with them first. Most will work with you to get you what you want... Roger
 
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Old 04-16-10, 06:16 PM
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If you're looking at an existing trailer and you would have to do the modification yourself and warranty wasn't a consideration.........

The towing of the trailer isn't likely to be affected by the changing of the spring perches from top to bottom (or vice versa), but there are two significant issues on doing this.

The height of the trailer is going to change by the thickness of the stack of spring leaves + the height of the spring perch + the diameter of the axle tube. If you're dropping a trailer you'll need the clearances to do that. Also the spring hangers are normally matched to the configuration of the spring/axle. They allow for the travel of the beam to the frame.

The other issue is the weakening of the axle tube. You would have a nearly continuous weld around the tube with the switching of the perches. However, you can fabricate a cap from a larger piece of tube, fit the perch to that cap and weld the cap to the axle beam with horizontal welds. This will get around the problem.
 

Last edited by marbobj; 04-16-10 at 06:56 PM.
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Old 04-17-10, 05:16 PM
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The height is the main goal, by putting the axle on the bottom of the spring the additional height will make the trailer tow closer to level with a 3" drop tounge.

I was not aware of a problem if I weld on a new spring perch... your opinion is that the heat from the weld will weaken the axle tube? I could actually just flip the whole works and used the existing perch, problem is that the axle usually has a natural arch that faces up.
 
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Old 04-17-10, 06:12 PM
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The camber arch has to go up. Otherwise, when loaded, the tires would be way out of wack.

Yup, on the .250 tube, which is the standard 6K axle (single rating) on down, a pair of welds at the same circumference line on the beam will weaken the tube. The way around that is the cap. I was in the trailer/trailer suspension industry for about ten years. The first four we built trailers, the last 6 I ran a regional distribution of suspensions for light to intermediate trailers and did a lot of the block work on problems with them.

Are you starting out with straight axles or 4 inch/6 inch drop axles? If the latter, you could switch the beams to straight axles and pick up a lot of height on the trailer. Do know what capacity the axles are (single axle rating)?
 
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Old 04-18-10, 07:25 AM
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It will be a straight single axle on a trailer rated at 3000#, probably a 2.5" diameter tube and 3 leaves on the spring. I had a 2000# Dexter on my last trailer and I just pulled it from above the spring and clamped it on underneath, no perches to worry about if I remember correctly.

Sorry that I don't have exact information, my last trailer was recently totaled and I have my eye on a new one that is supposed to arrive at the dealer very soon. My Dad has one like it and I have been going over and looking at his for ideas.
 
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Old 04-18-10, 07:38 AM
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Yup - the 3K axle is typically a .188 tube wall and often Dexter used a thinner tube with higher carbon content and a higher camber arch. You would not want to weld a continuous bead around that beam. There are also considerations as to trac/spring center which can stress that point even more.

As for alternatives, if no brakes, just idlers, you could probably get by with a spot weld on the outside of the perches to keep them in place. That would only be workable with no brakes.
 
 

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