Shake and shudder at high speed
 

From about 190 km/h onwards my car develops a lot of shuddering and gets marginally worse up to 230 km/h where I back off. Doesn't feel it coming thru the steering, more like from the rear end. (The steering wheel is not shuddering, the whole car is!)

Where do I start looking guys....give me a list (preferably prioritised.

Thanks
Mark

Wheel balance. I had a similar problem and invested $120 in a high speed on-the-car balance (Butler Tire in Atlanta). Actually, they balance the wheels off the car first...rotate tires on rims to achieve near perfect roundness (line up high spots in tires with low spots on wheels if any, etc.), and minimal weight required to balance. Then they are installed on the car and friction spun to 130 mph and tweaked on the car. There is a guage that senses suspension vibration and isolates area requiring weight. Had this done to both street and track wheels just yesterday.

I haven't driven on the track wheels yet, but with the streets, the wheel is as steady at 110 mph as it is at a dead stop. No vibration what-so-ever. Amazing. Highly recommended.