Need ideas on cause of front end shudder

[rsfdoc]

The vehicle is an '07 SRT Magnum with 6200 miles and F1 staggards. The problem is what I have been reading about on the forums for months. Namely, front end shudder/shake/shimmy at 80 to 85 MPH. Perfectly smooth at any other speed. It started to show about 2-3000 miles and has been force balanced 2 times by two different shops, (the first being the dealer but that's another story),with no real improvement. As an aside, there was a complete cure to the shake when the 255's were accidentally switched to the front (the other story). This morning I noticed a worsening (major wheel shake). The tires only had about 5 miles on them since starting out so I presume they were cold? After about 15 miles, it greatly improved but was still there. First time I really noticed this difference, but the first time I ever took it this fast that soon after starting. Pressures have been checked and maintained, lugs torqued sequentially, (thanks FC), and there is no visible abnormal wear. At a loss, anyone have any ideas besides new tires? Thanks.

[Hemi31]

Balance them again.I have had the best luck using regular clamp on weights on the inside lip and stick on weights behind the spokes.