Update - yesterday I moved the pivot arms to the furthest forward position which puts the trailer kingpin over the rear axle, where before it was 4" behind the axle. Don't know what difference that will make if any on adding weight to the front axle, other than maybe improving the ride somewhat. The tires are factory originals General Grabber HTS with 38k miles, probably about 65% of which was pulling the 34' horse trailer. The horse trailer was a gooseneck so the ball was 3" ahead of the axle. The cupping/scalloping of the center tread on the front tires showed up after I got the toy hauler - maybe just a coincidence. Due to the high cost to perform a correct tire rotation (front to back; back to front, dismount/remount& balance 6 tires, etc) on a dually, the only rotation that has been done is swapping of the front tires from left to right every 12k miles. I'm thinking that since the kingpin was 4" behind the axle, it may have been causing a rocking motion that is loading then unloading the front tires which may cause this wear issue, especially with the Ford Twin I-Beam front end. Just a shot in the dark though. Maybe just time to start tire shopping, but would like to resolve this issue before putting new tires on.
