Ray,
I did a post a week or two ago in the RV/hauling forum about Timbrens.
short version: great product the initial brackets were about 3/4 of an inch from the axle when bone stock, added on super hitch, tie downs, truck box and spray in liner. the timbrens had contact then and the ride was rougher but not bad to me, the boss complained so I e-mailed Murrey Biel @ timbren he sent new brackets and a 1 inch rubber spacer. When using the rubber spacer with the shorter bracket it would have been the same length as my original set up. so I mounted then without the extra spacer. They no longer have contact when empty (my empty is the above load), and the boss is pleased again with the ride.
steve