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Discussion Starter #1
I'm trying to figure out the math behind where to place the axles on a long 26-28ft deck single car hauler that will also serve as an ATV/motorcycle hauler at the same time.

Facts:
-Truggy weight is 5500lbs +/- 100lbs, and measures in at 18ft (126" WB).
-Two motorcycles that are 800lbs wet each, and come in at almost 9ft from tip to tip with 65-67" WB.

I haven't quite decided yet if I want to load the motorcycles on sideways or lengthwise, but I'm leaning more towards sideways and having a wide trailer (102" deck with drive over fenders).

Questions:
1. If I load the motorcycles on sideways I have the option of putting them either in front of the buggy and load the buggy on the rear over the axles, or I can load them behind the buggy and over the axles which would put the buggy more towards the front. Which is a better scenario for safety, proper weight distribution and smooth highway driving?

2. Assuming question 2 is answered, where to place the axles? I found I can get 7k axles for the same price as 6k axles, so assuming two of them with matching leaf springs and a 14k pound weight rating, what is a good rule of thumb for axle placement? My last utility trailer I built I ended up with a 60/40 split and IMO I would have been better off 65/35 or 70/30, with the axle more towards the rear. I'm always loading it front heavy to keep it from swaying. At any rate, let's assume this trailer is long enough to put the buggy and motorcycles on sideways, so 26ft deck + 4ft tongue = 30ft overall from hitch coupler to tail lights.

2.1. Figure the same scenario above, but loading up the motorcycles lengthwise with the trailer, which would make the trailer length 28ft deck + 4ft tongue = 32ft overall. How does that affect the axle placement?

As for materials, I have easy and cheap access to 6" 8.2# channel, 4x3" .250 wall tubing of long lengths, lots of 3" channel and pretty much any 1/4" plating for deck material all relatively cheaply. Time frame before I need this: about a year out. (moving across the country)

Check out PJ's 6" channel super wide trailer, as it's pretty much the basic layout I'm looking for but a little longer, perhaps with a dovetail on the end of their 22ft version.

http://www.pjtrailers.com/brochures/B6.pdf
 

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Discussion Starter #3
There are quite a few variables in the above equation that are still unknown.

15% tongue weight goal on an F250 class V hitch. Assuming motorcycles, buggy full of fuel and tools, firewood, grille and bird shit weigh 8000-8500lbs all together plus the weight of the trailer which is still an unknown...say 4000-4500lbs, that's 1800-1950lbs tongue weight at 15%?

If total gross weight is on the high side at 13000lbs, in that equation above with the axle placement at 20ft I get: X = (((1950lbs - 1300lbs)/13000lbs)*240") which then X = 12", so I'm supposed to move the axle forward 1 foot? On a 26 foot trailer with a 4 foot tonque, axle placement is 19ft from tongue coupler to center of between the axles? That leaves 7ft hanging off. Seem legit?
 

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I would put the center of the 2 axles ~10' from the back of the trailer. Then the truggy would more or less be centered over the axles. Then the quads in front. FYI 9" is considered wide load here. I would leave at least a few feet of extra space, that way you can move stuff forward or back to your liking. Which is also nice if you ever get different rides.
 

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Axle placement should not be dependent on load unless it is a static load (camper for example). Your trailer should be built based on the empty weights, then when you load you should load based on giving you about 10% tongue weight as well. That way your trailer is built for any load you may carry, not just the one you are thinking of right now.
 

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I'd probably load them up sideways up front and park the truggy behind. Do you have any idea what your F/R axle weights are on the truggy? If needed you could also put one bike in front and one behind. I'd set the axles at the standard 70/30 split and leave a few feet to move things around.

My setup is a 4,500lb jeep with a 1500lb (dry) pop up. I pull the jeep all the way up and the pop up axle sits right at the back of my 22ft trailer. This equates to about 1500 to 1600 lb tongue weight. My stock hitch is rated at 1500lbs if I remember correctly.

Why yours will have more tongue weight with the bikes out back:

Your extra 1,000 lbs is in the Truggy, most truggies aren't 50/50 weight split as my Jeep is, and your 1600lbs of bike presumably won't be right at the back of your trailer like my pop up axle is.

If your truggy is front heavy you may be able to back it on and leave the bikes up front. As someone already stated. Too many variables.
 

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My flatbed trailer had the axles way towards the rear and it was a 3500 lb trailer. 1000 lbs of tongue empty. Ridiculous. Was very hard to balance trucks and stuff and sometimes had to back rear axle onto the dovetail to keep from overloading the tow rig. If you go with a deckover you can make sliding axles like a semi truck. This also opens you up to sliding the axles forward to lay the trailer on the ground so you don't need ramps.
 

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Discussion Starter #10
I would put the center of the 2 axles ~10' from the back of the trailer. Then the truggy would more or less be centered over the axles. Then the quads in front. FYI 9" is considered wide load here. I would leave at least a few feet of extra space, that way you can move stuff forward or back to your liking. Which is also nice if you ever get different rides.
I'm assuming you meant 9ft not 9", but that's 108" so getting a trailer at 102" wide should come within legal limits when crossing state lines.

Axle placement should not be dependent on load unless it is a static load (camper for example). Your trailer should be built based on the empty weights, then when you load you should load based on giving you about 10% tongue weight as well. That way your trailer is built for any load you may carry, not just the one you are thinking of right now.
Definitely sound reasoning here.

He did put 102", presumably the bikes would be loaded at a slight angle
Yes at an angle if they're to be loaded on sideways but I haven't quite decided on that yet. It's so much easier to load by driving straight up the back of the trailer but having the trailer shortened is also a plus for backing up. The only reason I'd need a 102" wide trailer deck is for the motorcycles. Outside of tire measurement on the truggy is 78" (Ford D60 with H1's at 5" BS) and wife's XJ is 79" at the front axle (F250 D44 with H2's).

I'd probably load them up sideways up front and park the truggy behind. Do you have any idea what your F/R axle weights are on the truggy? If needed you could also put one bike in front and one behind. I'd set the axles at the standard 70/30 split and leave a few feet to move things around.

My setup is a 4,500lb jeep with a 1500lb (dry) pop up. I pull the jeep all the way up and the pop up axle sits right at the back of my 22ft trailer. This equates to about 1500 to 1600 lb tongue weight. My stock hitch is rated at 1500lbs if I remember correctly.

Why yours will have more tongue weight with the bikes out back:

Your extra 1,000 lbs is in the Truggy, most truggies aren't 50/50 weight split as my Jeep is, and your 1600lbs of bike presumably won't be right at the back of your trailer like my pop up axle is.

If your truggy is front heavy you may be able to back it on and leave the bikes up front. As someone already stated. Too many variables.
Truggy is a 3500/2000 weight split as it's back-halved and flat bedded. On rare occasions my wife's XJ might be put on this trailer instead of the truggy, which is a D44/D60 combo on 37's but she's almost a perfect 50/50 weight balance.
 
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