Help on bridge law formula for semi dump

I personally don't pull an end dump but a good friend of has been for years. He's got a 260" Pete with a triaxle 28' full frame. The problem with going with a shorter trailer is you run into problems with the inner bridge (drives to trailer) so you've got to have more rubber on the road to get to 80k gross.

 

Without knowing your location and whefe you plan to run its hard if not impossible to give you an accurate answer.

 

Iirc you should be fine at 38' l know a 26' is good for around 73000lbs gross on the interstate. I used to haul b-trains into Gary Indiana. Without a permit we would split them up at the mi-ind line. The lead was good for 80000lbs gross and the pup was good for 73 and change. The reason we were told was the lead was about 38' feet long to the rear axle of the triple. The pup was only 27'? To the rear axle of the tandem. So they trimmed the gross weight back. You also had to have the axles tight together to get the inner spread needed. Meaning a 26' pup with a 9' spread got its weight knocked back for that reason too. Don't take these numbers for gospel as its been at least 15 years since l ran trains into Indiana. Good luck on your plan. If you run into a mi-ind steel hauler theyll know all the ins and out of it.

 

Check this out and see if it helps or hurts
Indiana Bridge Laws / Vehicle Weight Laws | Dump Trucks
And this one
https://ops.fhwa.dot.gov/freight/sw/brdgcalc/calc_page.htm

 

As long as you have 51 feet between the center of your front axle and the center of your back axle you should be fine with 80,000

 

Figure 6

Now check axles 1 through 5 (Figure 6)
Actual weight = 12,000 + 17,000 + 17,000 + 17,000 + 17,000 = 80,000 pounds.

Maximum weight (W) = 80,000 pounds (Bridge Table for "L" of 51 feet and "N" of 5 axles).

Therefore, this axle spacing is satisfactory.