Curiosity question about weights....

If you’re wanting a general broad stroke then that would be the Federal bridge chart.

 

Depends on the state.

 

Each additional axle can carry X amount of extra weight (17,000 pounds, for example), but the whole vehicle/combination may or may not be allowed to go over 80,000 pounds gross weight limit. MI, for example allows trucks/trailers with enough axles to pull over 100,000 pounds on the roads, and maybe only during certain winter months, I don't remember.

A spread axle usually can carry more than that X amount of weight.
For example, each axle of a tandem set can carry 17,000 each for a tandem total of 34,000 pounds. A spread axle, say a minimum distance of 10 feet from the other axle can carry 20,000 pounds. The spread feature allows you to carry extra weight because the higher weight is not concentrated in just the distance between the front and rear axle of a tandem set of axles. The spread of the two axles doesn't harm the road as much as the tandem axle.

 

But now the why people like them (spread) so much in flatbed.

Try weighing 30500 with truck and trailer, carry a 49k coil. Misplace it by a foot and youll never axle out right even if by some miracle your tandems still slide

 

That’s not completely accurate. Its purpose isn’t to allow you to carry more on the spread. Its purpose is to better support concentrated loads, like a single coil. Because they’re further than 96” apart, they’re viewed as two separate axles (20K pounds each), which is what allows for the combined 40K pounds rating. Because the front axle is positioned further forward, that causes the spread axles to naturally carry more weight, over them. If one starts loading spread axles with the idea they can carry more over them, one WILL get bit and end up too heavy on them. DAMHIK.

 

That’s not true at all. A single coil off a foot is the same as the center of a full trailer load being off a foot, because you’re still dealing with a 1’ foot off-centered load. You’d still be able to move the tandems for a correction. The bigger issue is that single coil is going to make the trailer hammock so bad I would refuse to load it. If flipping a coil is the desired outcome, that’d be the way to do it.

 

Yeah, I'm obviously not a flatbedder. Thanks for the explanation.

 

No worries.

Because the axles are spread configuration and viewed as separate axles, you’ll often see a spread get “split” at DOT scales. They’re hoping to catch a faulty/incorrectly adjusted ride-height valve and being heavy on one of the axles. I used to regularly run over 79K pounds. Getting split was a regular deal. Any chance at nailing someone.

 

Go here and read ... it is complicated but if you get it, you will understand a great mystery and be a weight guru.


Hendrickson - Bridge Laws