Here's my two cents worth on loading or not loading the tires. I'm not for or against it but this is one scenario that has crossed my path. I haul dirt, rock or whatever in my trailer I tow behind the the tractor, when towing I can't have anything on the three point hitch for obvious reasons, but when I disconnect the trailer and attempt to load it I have to remember to scoop smaller loads in the bucket as to not go oops-ee-daisy when raising the bucket too high. I have several dings dents and splinters in the sides my trailer to prove it. Now before you dump all over me remember when your digging into that dirt pile that the ultimate goal is have that bucket heapin' good when you back away, it must be that macho thing. Something to do with power must overide comment sense sometimes. Now base your decision on a lot of comments you may read on this wonderful site and try and relate what would most likely fit your tasks for the loading or not of tires.
Steve