Unfortunately it is a well reported problem on many makes of car fitted with large wheels and ultra low profile tyres, there is just not enough give in the tyre wall to absorb the shock and the shock wave must go somewhere and it seems to be the wheels that take it, I too have the 19" wheels and very aware of the potential issues that you have, my old Porsche 718S had 20" wheels which looked fantastic but again no give in the tyre wall and the ride was so bad over poor surfaces, I purchased a set of 18" wheels and they transformed the ride without effecting performance .
