Why is it sometimes impossible to shut the trailer doors on sloped ground?

I don't see how the roof could carry some part of the structural load. Everything below the roof is below the roof.

Which part of the rear frame will tip forward, the top of the rear frame or the bottom of the rear frame? I don't see how it could be the case that the entire rear frame would tip forward.

First of all, let me discuss the fact that there are two types of possible slopes that a tractor-trailer could be on. On this entire thread, I'm discussing the situation in drawing A, not drawing B.

So let's clarify what you're writing about here when you write of a situation in which the drives and tandems are on ground with different side slopes. I'm 99% sure that you are writing about a situation in my drawing A below. But I like to be 100% sure.



Or are you describing the situation shown in drawing B below?



You say that each end of trailer wants to be parallel to ground, and the trailer structure twists. I have several questions about that. I think that this is the key issue here, and I am confused about it. You're probably smarter than I am. I need you to explain it to me like I am a five year old.

In all the questions in this post below this sentence, I am only asking about the situation in drawing A.

When you say that each end of the trailer wants to be parallel to the ground, do you only mean that the front (nose) end and the rear end of the trailer want to be parallel to the ground? Or do the side "ends" of the trailer want to be parallel to the ground too?

Why would each end of the trailer wanting to be parallel to the ground cause the trailer structure to twist?

Which direction does the trailer structure twist in in drawing A?

 

Then why didn't any of you giving a decent explanation in terms of physics before Hammer166's post? Why did you all just beg the question?

 

I (apparently erroneously) thought that Hammer166 was saying that the roof carried part of the load of the entire trailer. My apologies.

Could you answer any of other questions I wrote in post #108 please?