Michellin Lattitude Run Flat Question

[taosx5]

Hey all, I have searched the forums and can't find anything on this but maybe someone has had some experience they are willing to share.

I have an 03 4.4 and 04 4.6, both are E-53's. I found what I thought was a pretty good deal on OEM wheels and tires. The wheels and tires came off an 07 E-70 3.0 (255 X 55 X 18). The tires are Lattitude HP Touring Run Flats. I have seen this car since it was new so I know it was well taken care of. The owner bought after market 20" wheels so he kept these in his garage for the last 5 years. The tires had maybe 10-15 thousand miles so there is lots of tread left on them. I bought them to have a dedicated snow tire and wheel for the wife's 4.4.

Here is the deal! I had them all balanced and put them on the 4.4. Afterward there was a small vibration in the steering wheel at 45 to 55 mph. I figured it had to be a problem with one of the front wheels so what I did was take one of my old wheels and tire with me to a section of highway where I could change them one by one to see if I could determine the problem wheel. I started with the left front and swapped the new one with my old then drove it a few miles at speeds from 0 to 90. It seemed like the vibration never went away no matter which new wheel I switched out. I determined that the left front (the first one) probably had the best ride meaning the left front may be the problem tire. So I put it on the rear and the vibration in the steering wheel at 45-50 mph is still there. I even played with the air pressure and ended up running 32 F and 34 R.

My wife said she wanted her old wheels and tires back. I decided to swap the two rears but left the new ones on the front then drove it. The vibration was still there. So I went ahead and switched the fronts out to the old ones. I guess I will probably run these new wheels on the 4.6 as a winter tire and wheel until I need to replace the Michellins to a dedicated snow tire.

MY question is what is the deal? Do these Lattitudes just need to be run a while to get dialed in? Is there a way to get rid of this vibration completely cuz it does go away at highway speeds. Do I need to worry about it messing up my front end or alignment? Any help or advise is much appreciated.