I have several ford vans. Two 1/2 tons and 2 one tons. For years I would put new tires on and the van would be smooth for about 6 thousand miles, then the front tires would cup ever so slightly and I would rotate them to the back. This summer I was having trouble with both one ton vans shimmy in the front end. I swapped the front tires (drivers to passenger) and the vans smoothed out at highway speed. My conclusion is that the twin I beam does cause some wear on the inside tread of the tire and so the tread blocks wear high on the front edge and more on the back edge. I do brake hard and often from speed, I do a lot of highway driving. By swapping sides the block pattern is reversed and immediately the front wheels that felt out of balance began running perfectly smooth. Over the next several thousand miles they get smoothed out to normal and even tread.
If you are having trouble with what seems like balance on the front try switching the front ones and see if it helps. It doesn't take much tread wear on these vans to make it shake. Hope it helps someone. Andrew.

 

Andrew this is a good observation and no doubt helpful in the short term for anyone with similar issues.

I disagree the I-Beam suspension causes uneven tire wear by its design. I'm running two E250's (2000 & 2003) both with rebuilt/solid front suspensions using Michelin LTX 245/75-R16 tires with absolutely no measurable wear skewed to the inner or outer tread. One with just over 60K miles on the tires, the other just over 32K so far.

Inside tread wear strongly suggests an alignment issue.

 

Toe or camber is off. Possibly due to worn parts.

 

The Twin I-Beam design cannot maintain a constant camber angle during suspension travel just by the way it works. Our fleet always wears the inside edge and cups the front tires. As long as we rotate vigilantly it's not a huge problem. However I hadn't considered right to left front rotations. That could be helpful to try. Our Chevy Express vans have double wishbone front suspension and do not have this issue at all and almost don't need rotations.

I know the inside edge wear on our tires is due to camber angle not being set correctly for the loads we run. A few years back I tried to get the alignment shop to intentionally go outside the specs and set a camber that would reduce inside edge wear however they refused to do it. One of these days I might revisit it since it is does cause us to discard tires earlier than we would have sometimes. I would think the Ford alignment specs assume a loaded van however maybe we need to show up at the alignment shop with 2000lbs of sand bags in the van for them to get it right.

 

I'm not sure how my use of various E-Series differs from most other users, DelGriffith's situation completely apart from most who post here. I've yet to have any excessive tire wear issue over four different E250's ranging in model year '97 to 2003. Two of those run empty much of the time, the others loaded just under their GVWR as daily drivers. Three of them running Michelin LTX 245/75-R16 E-Rated tires.

I have been somewhat meticulous in maintaining a sound front suspension which includes new urethane axle pivot and radius arm bushings along with Moog greasable ball joints. I am a bit lax in tire rotating but still have across-the-tread even tire wear after 60K miles in one instance.

Given my own small sampling of good luck I'm onto something---just not sure what?

BTW every alignment has been set to Ford's specs with regards to camber and tow, the cross-camber also being tight to those same specs.