I may be wrong here, as i am learning about heavy haul but I think what the thicker shims do is cause the load to put more weight to the trailer axles. It cants it backwarda forming more of arch like a bridge. When they run booster axles with spreader bars in between they have to do the same thing. it just depends on where you need to shift the weight to. I might be wrong. some one please correct me if I am. Im only experienced on 7 axles right now so these shim dont really apply to me, but I should be learning this stuff hands on soon hopefully.
No idea, I don't have to do this on my Murray 50T. I have fixed tandems, so you may be right. EDIT: You are correct, I saw another video on shimming for weight transfer.
