OK, I've just quickly skimmed through all 33 pages of this thread. Probably missed a few pertinent pieces of information in the process. Barring that - there are a few things that come to mind with respect to the axles.
The flexrides can be welded in the middle before the cartridges are inserted without potential damage to the rubber, the Dexters can not. Flexrides have a shorter torsion arm than Dexters. That may be a factor in why some scrub and others do not. Flexrides have a greater recommended down angle than Dexter; 24 degrees vs 10 degrees. The arcs created during motion will differ.
Comparing pictures of the various axles with tires
off - taken from the side of the trailer may give some insight to the problem and possible solutions.
At what down angle were the flexrides set at? What is the down angle of the Dexters. How were the trailers that have the problem configured. E.g. Make? size? down angle? tire size? rim offsets? Etc. Are the bodies placed in the same position relative to the frame? Axles to frame? Axle
Knowing the details one can go back to the axle
manufactures web pages and determine the range of motion. Dexter engineers will give you printouts of this type of information including tire sizes.
Attached is an example of what Dexter gave me for one of the possible axle
configurations on my boler
American. Note the recommeded 3" clearance around tire diameter on page 2.
I believe I went with this configuration because there was only 0.10" front to rear tire shift between full load and no load. Using the 10 degrees as recommended gave 2.4" up and down movement between no load and full load and 3.34" total for shock load. Doing the math, there is a bout a 1" bounce range to absorb shock.
One should also read the disclaimers on the 5th page as they state a number of variables.
I believe I did catch mention of the tires
changing shape at different speeds, pressure and temperature. I seriously doubt that would matter if the 3" recommended clearance was initially provided. The question now becomes how best to fix a design flaw.