i've got a steering wheel vibration that comes and goes. the car is a
87 300D w/ 245,000 miles. i have new yokohama avs db tires that are wearing perfectly, so i know that my prevous alignment problems are gone. (but the car did this on the last set of tires, too). the most consistent cause seems to be outside temperature - when its sunny 90F+ after the car is all heated up (50 miles into a 200 mile trip from nashville-knoxville) the vibration will be there at its worst and I will see the steering wheel vibration (and also feel it/hear it towards front of car - nothing thru the seat). on the very same return trip, when its cooler outside 80F and the sun has gone down, the vibration is less, the road, the steering wheel does not visbily vibrate. some inconsistent patterns -
it seems to do it without regard to road surface, but older roads can be smoother.
- hard acceleration on a freeway seems smoother (e.g. after the car has been stopped to buy a Coke)
- sometimes a left or right curve can make it stop
- seems smoother at 60 mph than when faster (69-80)

I don't feel its the tires or wheels, nor does my mechanic. Different tires and wheels do the same thing. Tie rods, drag link, steering damper, all control arm/link bushings have been replaced within last year to cure other issues. Wheel bearings have never been replaced. Front left wheel bearing tightened twice (loose), right wheel bearing tightened once. If the car is jacked up and front tires pulled at 12/6 or 3/9 the wheels are tight (except when the bearings needed tightening).

is it sensisble to think the wheel bearings should be replaced? any ideas?

thanks,
Brian