I have an 88 760 wagon with roughly 210,000 miles on it (odo was dead for a brief while). The tires on it are Sava rapidexs (http://www.sava-tyres.com/eng/samx.exe?script=dezen.sam&a=detail&pojdi_na=8 for more info) which are rated for 60,000 miles. I changed all four at once about a year ago and they have roughly 15,000 miles on them. I've followed the rotating schedule not religiously, but pretty closely.

When I drive to around 25-35 mph, I feel a slight shake in the steering wheel (not just a vibration, the wheel is discernibly moving left and right, albeit only slightly). Notably I don't feel this moving at lower speeds. Also, I get something similar to this around 73-80 mph, though it's hard to tell if it's actually a shake or just a vibration since at that speed I wouldn't really be able to discern individual movements. I also notice a slight bouncing every so often; particularly at night when the lights on the stereo make it evident. Also, not that I do this on a regular basis but I noticed last weekend that at 100mph, the ride was surprisingly very smooth; much smoother than at 75 or 30mph. Again note that the tires are H rated and it's very rare that I go that fast, and when I do it's for brief stretches just to pass or something similar)

I have had these symptoms before, and in that case it was tread separation. The tires, however, were pretty old at that point and in fact had severe visible wear (I was very new to car ownership at the time and have since wised up. My current tires are not exhibiting any unusual signs of wear) Also, the symptoms were much more severe, and I could feel the wheel move back and forth as the car rode over the bubble in the tire even when I was just creeping forward).

Is it possible that I am detecting a nacent case of tread separation? Could the tires simply be out of round? Is wheel balance a possibility? My main concern is to determine whether or not there is tread separation as I most definitely do not want to kill myself. I first noticed these symptoms about 2 weeks ago and after the first couple of days they haven't seemed to get any worse or better, but I've also only driven about 20 minutes every couple of days since then. For what it's worth the car sits for a lot of it's life (I usually make either 300 mile trips or 3 mile) and I was wondering if perhaps that could cause the tires to flatten. I've checked the pressure and tried them at both what the manual recommends (28 front, 32 rear) and slightly higher.

Lastly, I had the tires rotated about 2 weeks ago (I noticed this problem just about a day before I had them rotated, actually, and didn't think to ask about it) and the tire shop didn't happen to mention anything unusual about the tires, but I didn't ask either.

Thank you in advance,
Bob