Car wobbles ALOT

Soo, i have 2001 Pontiac Grand Prix SE 3.1L V6. When you sit in the back, it feels like your on a RolerCoster, the back of the car wobbles really bad. My dad thinks its the brace in each tire that came lose on one of the back ones. Help me out, and give some suggestions to what could be wrong:banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead: :banghead:

the back of the car wobbles really bad.


** the back of the car wobbles really badLY **

How old are the tires? I would look at the back tires as someone slowly drives away. It may be belts in the tires that are separating due to age. It happened to me once.