What I was actually thinking of was that the carcass was not concentric with the outer tread surface. I can't think of any way to wear a perfect tire to get what GSTom described. I'm suggesting the tire could have been defective.

If the tread rubber was a constant thickness when the tire was new (which it should be, ideally) then the total circumference of the tire should wear evenly.

Since the final condition of the tire was to have 0.0" of tread for 2/3 of the tire, and "acceptable" tread depth for 1/3, then something had to be out-of round, somewhere.

The minimum base gauge (from the bottom of the rain groove to the top of the plies was likely .06" or so, plus the depth of the groove itself (hopefully .06 or so, according to Lincoln's scalp), for a total of .12" or 1/8" tread.

Just the variation in tread depth, and therefore mass, *should* have created a noticable vibration.

**** sorry for the long-winded explanation ****