Why are the tires so far back, increasing tongue weight.

[Dutch61]

While investigating goose neck flatbed trailers, 25+ feet deck and longer, I noticed all of the design have the 2 or 3 axles way far back. Is this a stability issue? Why not move the axles a few feet forward to allow for more flexibility in load placement? Why not place them midway under the main deck?

 

[Depmandog]

While investigating goose neck flatbed trailers, 25+ feet deck and longer, I noticed all of the design have the 2 or 3 axles way far back. Is this a stability issue? Why not move the axles a few feet forward to allow for more flexibility in load placement? Why not place them midway under the main deck?

There is a formula that trailer builders use to determine axle placement, and it all hinges on center of gravity of the trailer, and what percentage of the load you want in front of your axles.

Find the center of gravity from the hitch back then divide this number by the percentage of the load you want in front of the centerline of the axles - this number is the distance to the centerline of the axle(s) location.

This setup ensures that an empty trailer will tow properly. If you have some specialized hauling application - you could have the axles mounted on a sliding / adjustable rack that would let you move the axles forward to accommodate your load, yet still able to be rigged to tow properly when empty.

 

[Turbys_1700]

I am not sure what the formula is for goose necks versus fifth wheel campers but I think that the tongue weight ratio is 20% for fifth wheel's...
If you have a 14K goose neck that would put 2800# of the hitch at max weight...
You need that weight on the tongue to make sure that the trailer does not "wag the tail"...
Too little weight on the tongue will do that...
I am thinking that the ration for tag trailers is 15% but don't hold me to that...

 

[RDrancher]

My Big Tex GN was built in 1996. The tongue weight is higher then current models from the same manufacturer. Apparently they've revised their formula over the years.

 

[Diamondpilot]

Nothing worse than a trailer with too little tongue weight. Getting it right is a art. I can tell you from experiance that pulling between 14,000 & 25,000# the further back the axles are the better it pulls. The truck bucks less and it tracks very nicely.

My 18,000# tri axle bumper pull boat trailer towes like a dream compared to a 10,000# camper. Axle placement is a huge part of this.

Chris

 

[Diamondpilot]

Nothing worse than a trailer with too little tongue weight. Getting it right is a art. I can tell you from experiance that pulling between 14,000 & 25,000# the further back the axles are the better it pulls. The truck bucks less and it tracks very nicely.

My 18,000# tri axle bumper pull boat trailer towes like a dream compared to a 10,000# camper. Axle placement is a huge part of this.

Chris

 

[CDN Farm Boy]

Tag trailers generally are in the 10% range for tongue weight. Proper tongue weight is much more important on a tag trailer as the margin is smaller and you have the lever length from the rear axle to the hitch to compound the problem. GN hitch is actually mounted an inch or two infront of the rear axle to help combat the wagging trailer problem.

Further back axles make the trailer steer slower (and easier) when backing up than same length trailer with closer axles.

I used to have a 25' GN flat deck, 14' GN enclosed and 20' GN stock trailer. The flat deck, regardless of weight on it towed like a dream, the stock was decent and the enclosed was a pita. There is no difference in formula between GN or 5th wheel, same as there is no difference in formula between a tag with ball or pintle.

 

[RedNeckRacin]

In reality a 25+ plus long trailer is most likely not going to be rated for anywhere near 10k so that puts it in the realm of the HD pickups and medium duty trucks which would have no problem with the weight if sized correctly. before I get flamed I do know that the newer half ton trucks keep getting rated for more and more weight. I would however think you would be criminally insane trying to safely tow a 25 ft+ tandem dual gooseneck with one.

Tongue weight also equals traction! :thumbsup:

 

[muddstopper]

The formula for figureing axle placement is to place the center of the axle one inch back for evey foot in lenght of the trailer bed. Ex. If you have a single axle trailer with a 10 ft bed, the axle would be set back toward the rear of the trailer 10 inches of the center of the bed, or 5ft 10in from the front of the trailer. If you have a two axle trailer of the same lenght, the center of the two axles will be at the same 5ft 10in from the front of the trailer. For longer trailers with 3 or more axles, you would use the same formula for placing the center of the axles in relation to the center of the bed lenght. This will result in an even 60/40 split for the proper tounge weight.

http://www.trailerplans.com/index.php?option=com_content&task=view&id=40&itemid=29

 

[saltbranch]

I have always wondered the same thing. A G/N trailer with a dovetail are further back than a straight deck trailer of same length. I have never put a tape to it, just appears that way. One reason I can see is that when loading equipment is that there is more support in the back help keep the front of the trailer lifting the pulling vehicle off the ground. On my 40' flatdeck, I had 11' HD ramps, loading a big JD tractor, as we went up the ramps, it start to lift the rear of my dooly off the ground. Plan B, i made some brace's to fit each corner of the trailer that would drop to with in 10" of ground, as i loaded my stops would hit the ground and good to go.
Funny story, I was pulled into Ft Hood and we were loading fuel trailers. 2 drop deck trucks and me in my GN. Well the big trucks backup to the dock, forklift drivers drove the trailer. My turn, i back in, set my brakes. i motioned for the loader to wait. I was getting my drop legs to position them to be loaded. next thing i know the back of my dually is in the air and rolling forward. i had vac/hyd brakes and reached in window,pulled the ebrake handle, locked the trailer brakes. At this point the fuel trailer and front half of forklift is on my trailer, the counter weight of forklift was the only thing still holding the rear of the fork lift up. the forklift driver was stressed to say it politely. Brought in a bigger forklift to lift the forklift off my trailer.
My thoughts are thats why the dovetail trailer have the axles set further back than a straight deck trailer