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Old 11-25-2023, 01:16 PM   #1
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Question Over or under

2014 Eagle HT & 2012 Ford 350 w/ air bag suspension. B&W hitch. The RV tilt is pronounced/observable on front end when towing. I have heard that moving the springs over to under the axle will help leveling….. Also heard it can increase maneuvering, tip-over, & other issues. Opinions?
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Old 11-25-2023, 09:16 PM   #2
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Over slung vs under slung. You would not notice a difference if you changed to over slung. You'd gain the same height as your axle diameter. Likely 3". A lot if not most RV trailers a built over slung. Usually old trailers or later high end high profile are under slung. If you need the extra height and have the over head clearance to allow for it, go for it.


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Old 11-27-2023, 09:30 AM   #3
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If you have the axle over the springs and are towing nose-high, switching the axles to under the spring will lift the trailer to reduce the nose-high condition.

Yes, because you are lifting the trailer, the center of gravity is higher which will make it sway more in a cross wind and more tippy when cornering (that's fact, not opinion). My opinion part is it's already 12' tall and 30+ feet long, 3" of height probably won't be a world of difference.
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Old 11-27-2023, 11:03 AM   #4
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Originally Posted by Mopar_Earl View Post
Over slung vs under slung. You would not notice a difference if you changed to over slung. You'd gain the same height as your axle diameter. Likely 3". A lot if not most RV trailers a built over slung. Usually old trailers or later high end high profile are under slung. If you need the extra height and have the over head clearance to allow for it, go for it.


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While it would seem like you gain the same height as the axle diameter, you actually gain the axle diameter plus the spring's thickness. In this case I snagged an image from Etrailer and this is a 3500lb spring (7000 axle) and the thickness of the spring where the axle mounts is not specified (although they do list all the lettered dimensions), but I suspect around 3" for a spring like this one.

So with a 3" axle and springs like this (just guesstimating 3" as well), you would be raising the RV around 6" if you mount the axle below the springs vs above the springs. ~CA
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Old 11-27-2023, 11:21 AM   #5
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Originally Posted by Eldecker View Post
2014 Eagle HT & 2012 Ford 350 w/ air bag suspension. B&W hitch. The RV tilt is pronounced/observable on front end when towing. I have heard that moving the springs over to under the axle will help leveling….. Also heard it can increase maneuvering, tip-over, & other issues. Opinions?
Unless my mind is taking a break today, if your RV trailer springs are already over the axle then moving the springs to be under the axle will lower the trailer where the axles are making it even more nose high in the front. I am suspecting you are saying the trailer is higher in the front which would mean having the axle below the springs is what you want (and it sounds like you already have that?). ~CA
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Old 11-28-2023, 08:22 AM   #6
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Originally Posted by craigav View Post
While it would seem like you gain the same height as the axle diameter, you actually gain the axle diameter plus the spring's thickness. In this case I snagged an image from Etrailer and this is a 3500lb spring (7000 axle) and the thickness of the spring where the axle mounts is not specified (although they do list all the lettered dimensions), but I suspect around 3" for a spring like this one.

So with a 3" axle and springs like this (just guesstimating 3" as well), you would be raising the RV around 6" if you mount the axle below the springs vs above the springs. ~CA
Correct, I failed to mention that. I don't recall what the spring pack thicknesses are. Could vary well be 3 or even more.


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Old 11-28-2023, 08:25 AM   #7
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Originally Posted by craigav View Post
Unless my mind is taking a break today, if your RV trailer springs are already over the axle then moving the springs to be under the axle will lower the trailer where the axles are making it even more nose high in the front. I am suspecting you are saying the trailer is higher in the front which would mean having the axle below the springs is what you want (and it sounds like you already have that?). ~CA
Good catch. I reread the post and sounds like he is wanting to change from overslung to underslung, which would drop trailer height.


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Old 12-11-2023, 10:53 AM   #8
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Thanks all. Yes, from under to over. 3" plus 3" spring thickness would be 6" total. Hopefully the cross winds / center of gravity issues won't be too much. The front is currently very pronounced in height.
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Old 12-16-2023, 03:55 PM   #9
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On my Eagle Ht the springs are over the axle, U-bolts holding them in place, putting the trailer weight on to the axle. I would think having the springs under the axle the weight would be on the plate and nuts.
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Old 12-16-2023, 04:40 PM   #10
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Any way to adjust the hitch/ride height to change the trailer towing characteristics with regard to center of mass?
Just my $.02...
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Old 12-16-2023, 06:35 PM   #11
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On my Eagle Ht the springs are over the axle, U-bolts holding them in place, putting the trailer weight on to the axle. I would think having the springs under the axle the weight would be on the plate and nuts.
Yes. The conversion kits recommend welding the plates, and not just rely upon the U-bolts and nuts.
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Old 12-16-2023, 06:51 PM   #12
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My 2019 Eagle HT Fifth Wheel/F350 combo rides a little high in front. it’s not a problem it tows great. Since the springs are already over the axle I guess adding blocks could help level it out more. I think maybe it’s not worth the trouble.
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Old 12-17-2023, 07:45 PM   #13
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Any way to adjust the hitch/ride height to change the trailer towing characteristics with regard to center of mass?
Just my $.02...
^^This. Unless you are trying to address a ground clearance issue as well, the best way to level the trailer is to adjust the hitch height.
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Old 12-20-2023, 10:15 AM   #14
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My 2011 Eagle 321RLTS came with the springs on top of axles and sits fairly level when hitched to my Chevy CCLB dually. I did move the bolt holding the springs one bolt hole to raise the rv when I put the heavy shackles/wetbolts/bronze bushings a few years back. I just don't have any issues with towing.
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Old 12-21-2023, 08:29 PM   #15
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^^This. Unless you are trying to address a ground clearance issue as well, the best way to level the trailer is to adjust the hitch height.
That works till you hit the bed. Bed clearance is needed and priority followed by leveling.


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