Just bought a 2002 SC430 with 32K miles for my wife. Nice car. It came with worn out run-flats. I replaced them with Continental Extremes. Original rims. The car has a steering wheel vibration between 55 and 60 mph. I brought it back to the installation place (very reputable). They road force balanced all 4 tires (3 were out) and brought them all back to specs. They checked the tie rods and said they were ok. The steering wheel shimmy is still there. They are at a total loss as to what could be causing it. My next step would be the Lexus dealer but I wanted to see what you guys, who have had this car for a while, think.

 

This thread should help you out

https://www.clublexus.com/forums/sc-...he-shakes.html

 

You may have square wheels my friend...

The RFT's have little or no capability to absorb bumps, so you may find that one of your wheels is misshapen.

If the shaking is coming through the steering wheel its your front, if you can feel it under your seat its the rear - if you've got a combination etc...

Take it to an alloy wheel specialist, they will see which one it is and either repair or recommend you replace if its too bad.

You can do a quick check yourself, by putting car on a jack and fixing a point (pen, pencil) next to the outer wheel rim and rotating it by hand you will quickly see how round the wheel really is.

To give you an idea, its around 50 UK Pounds to make a square wheel round.

I actually have a problem with the shape of one of mine at the moment, but its holding air (check your air, as this is a sign as well) and I have no balance issues at all, but the tyre-shop used an awful lot of weights to get it right...

 

I called Discount Tires and they agreed to replace the Continental Extremes with a new set. I'll have them installed and balanced and see if that fixes the problem.