I have a 2013 Luxury RWD 3.6 ATS with 21k miles. Bought it with 9k miles about 8 months ago. It has the original Michelin Primacy run flats which still have pretty decent tread. I noticed over the past couple months that the car jumps/slides when I hit bumps, especially at higher speeds. It feels like I'm driving on marbles. Wife says if feels like hydroplaning. I also have been feeling the bumps quite a bit more lately too. The ride has gotten pretty rough. Would you think these are symptoms of the run flats aging or potential suspension problems. Thanks in advance.