My car 1990 300E 4mat had new Continentals put on at the time of purchase, so I dont really know if the problem pre-existed these tires.

The steering has always vibrated a little at hwy speed...but as it worsened and then became unnacceptible, on this forum's recommendation I sought out a tire place that had the Hunter 9700 GPS. They were sure of the problem being fixed, even got a very fancy computer printout that supposedly confirms the balancing results, but no real improvement. I even .

I found my spare to be in perfect (unused w/ a virgin 15 hole rim, to my surprise) condition, and noticed that the lead weights were factory installed ON BOTH THE INSIDE AND OUTSIDE of the wheel...so out of curiosity i looked under the car and found the newly installed weights only on the outer rim, and none have any inside weights....does this make sense? Not to me..considering the vibration is still there!

So either they're out to lunch and I find a better shop, or I have to find another vibration source...all my shocks are recent, maybe a very slight alignment problem but certainly nothing too obvious.

I drove it today on the hwy w/ the usual vibration. I slipped the car into neutral for a few moments, no difference in feeling even as the engine quieted down to idle.

Any thots?

I used to get weights put on the inside only for cosmetic reasons...but this was for a show VW Beetle, that for the most part saw the lower end of highway speeds.

You CAN get lucky with some rim and tire combinations, but usually, the only real way to ensure that your tires and wheels are perfectly balanced is to mount the weights inside AND out.

Once you can safely rule out a wheel balance problem, if the shimmy persists, then perhaps suspension or driveshaft components could be the culprit...

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Seems like they blew their training budget on the machine! The dynamics to correct are pretty simple. An imbalance can be modeled as a net mass located between the inner and outer rim of the wheel and at a certain radial distance from the center, and at a certain rotation from an arbitrary reference radius. This will require the weights to be split between inner and outer rim in some ratio - but not zero. I.e. the imbalance will never happen to find itself on the outer circumference of the tire.

Steve