Experienced exactly the same! Got the car delivered on summer tyres - no problems at all! After changing to winter wheels, the behaviour of the car changed. Like driving on rough tarmac, and vibration at speed above 90 - 100 km/h. Thought it had to do with the tyres or the rims, and contacted the Lexus-vendor. After testing they concluded that the problem had to do with some kind of dampers that now will be installed nexr week. Hope it works. They also told me that this was a known issue also from other IS300h