Getting axles to scale

I get what you're saying now. I've never worried about that. Maybe I should

 

I can't tell if your 5th wheel is adjustable, but I'd remove that toolbox and slide the trailer up onto the tractor a little more. Hauling more weight over the rear axles makes you feel like your dragging an anchor.

 

There are some states that will weigh each trailer axle and write you up for a axle being overweight.

 

Read the wording of the regs. They’re single axles. You get up to 20k apiece, not 40k on the pair. If you’re 40k on the pair on one of those trailers you’re fat on one of them, I’d almost guarantee it. I had a 48’ 10’1” here for a while. Out of 7 tractors in the yard not one of them could load the forward axle to 20k without putting at least 23k on the back. I get the idea for loading big coil on US weight. Bias it to the rear and if you miss by a couple of inches you’re still ok on the back. Just seemed like a ridiculous amount of tire wear for nothing to me. I can put 37,400 on a 54” tandem here.

 

It seems a touch counter-intuitive, but moving the boards (or adding boards in more places) doesn't change the weight distribution of the load on the trailer. Yes, moving the board forward puts more of that board's weight onto the 5th wheel, but it also reduces the percentage of the load weight that board is carrying. Only moving the load will change the trailer's weight distribution.

@Lazer 's post encouraged me to dust off my 25 year-old statics skills, and do the math. Moving the load that 1 1/2' forward will only move about 1700#, so not enough to help you if load 50 footers. You need to get that front trailer axle to carry more of the load.

The problem is the arch of the trailer causes the front airbags to extend too far. When that happens, they have a smaller area to push against than the rear bags, so the same pressure in each results in differing loads on the air springs. I've never pulled a spread so I've not done it, but it always looked to me like there should be a spacer for the front bags so that both sets of bags were operating at the same height from piston to top plate. That should ensure both axles of the spread were carrying the same load. Double check and make sure there's only one height control valve, too. If there's a valve on each axle (uncommon) it can cause this imbalance.

EDIT: Almost forgot to add, make sure the truck suspension height is correct. If it's a touch high, it exacerbates the overextension of the front bags.

 

They will also ticket you for the unsecured wood between the landing legs.

 

Make sure the trailer ride height isn't too high, as well.

In a perfect world, it should have zero effect. In reality, if there's any change in 5th height from the slide, it could change how much weight that front axle of the trailer is carrying. It won't be much, but there may be slight changes.

It's not. You're changing spring rates in the racecar. Changing the height of the load above the deck has little effect. You have to move the cg of the load, and you'd have to raise the rear several feet to move the cg forward more than fractionally.

 

Moving the 5th wheel forward adds weight to the drives and the front axle (not much to the front unless improperly loaded). Personally, if I need to adjust mine, it’s about 500lbs per notch and each hole on my trailer is worth about 250lbs. To me, it looks like your trailer isn’t riding up on your tractor enough. Sliding the 5th wheel will remove weight from the trailer.