The 5th-wheel and trlr-tandem weight off-set

You gonna get a lot of differing answers on this. Most are rules of thumb or scientific wild-### guesses. Only way to know with 100% accuracy is to weigh on a scale, make your adjustment and reweigh. Then track all those adjustments. That being said. I was told one rule of thumb was ~200lbs per slot on the 5th wheel. However not all 5th wheel makes have the same distance to their slots. For the trailer I use this app called the "Trucker's Slide Calculator". It seemed to be "close enough for hand grenades". YMMV

 

Too many variables can change the actual weight moved.

Here’s an old thread on the subject that does a great job of explaining it.

Tandem Setting Formula

 

I always told my guys each hole moves between 200 and 250 pounds, but it varies based on how the trailer is loaded and how close you are to the balance point.

Imagine a trailer loaded with 24 pallets. The first 6 weigh 4,000 each, the last 18 weight 1,000 each. If you scale with the tandems all the way back, then move up 1 hole and reweigh you'll probably only shift 50 lbs or so. If you keep moving up 1 hole and scaling you'll find the each hole moves a little more.

Now put the heavy pallets all the way back and redo the experiment. You'll move a lot of weight in the first few holes. The amount of weight per hole will decrease the further you slide.

Finally, put the heavy pallets in the middle. Again, the first few holes won't move much, but the weight per hole will increase until the weights are balanced. Then the weight per hole will begin to decrease.

 

I would be willing to bet that over 75% of all carriers have disabled 5th wheel movement. I understand the question, but in all honesty, unless you are experenced I HIGHLY recommend agaisnt moving that 5th wheel at all. Back in my driving days, when I live loaded, I did my best to see where the last pallet was in my trailer. That was where I set my back tandem. Most of the time, that would be the perfect spot. In addition, if a rather heavy pallet is sitting closer to 8 feet from the doors, there is a good chance you will never be able to get that load legal.

When it comes to picking up an already loaded trailer, I HIGHLY recommend paying close attention to what @Concorde wrote and @gentleroger 's first sentence above.

It has been almost 14 years since I was last on a CAT scale, so I have no idea what a reweigh costs. Since the company generally pays for this, just take your time and figure out the numbers on a case-by-case basis.

Thankfully, most of the time the person live loading the trailer has some experience and will load it correctly. The loads that frustrated me the most were places like Budweiser, when they would not put enough spacers in the front, and this caused a situation where you could not get the load legal. Budweiser uses robots to load. I remember many times having to drive back to the loading dock and having a human fix the load.

Over time and experence everything I just wrote will become muscle memory. If you load at the same places a lot, you will know by memory where to set the tandem.

 

My Trucks general rule seems to roughly be 450lb for fifth wheel, 250 per hole on trailer. Assuming you’re sliding because your grossed out (44-45k in dry van) and loaded evenly. In which case, rear of wheels or mudflaps even with the rear of load seems to work best. Hope this helps with a rough idea where to start. Best to find a good spot for fifth wheel, and leave it. On my old Classic, it’s one notch forward of center of slider. Avoids damaging fairings when jacking it around past 90 degrees, and still helps with fuel efficiency w/close enough gap, and still rides good. Keeps enough weight on steers, while minimizing bucking. Every set ups different. You’ll figure it out.

 

i use that same app. On my truck it seems it's a bout a hole off. If it says move 5 holes, I move 4 and usually am spot on.