Vibration and bouncy even on smooth roads

[OutKlast]

My car has this annoying vibration to it that starts around 35mph on up. Its not the roads I live in FL and I know Camaros have rough rides I'm not concerned with feeling bumps on crappy roads. I drive 50 miles roundtrip highway on a regular basis and most of that is wide open 4-5 lane flat freshly paved highway thats butter smooth yet when I get on it; it feels like rippled water. Same with below that my wheels are balanced I feel it on my 18"'s and I felt it on my stock 16"'s. It's really starting to drive me crazy if I look over the passenger seatbelt buckle is just shaking like crazy especially when I go about 70 but it reduces past 90. I just want to have a smooth high speed ride what could be causing this?

[Dominic]

Have your tires roadforce balanced, not normal balanced - it helps a lot. Then, be sure your alignment is in spec.

Mine vibrated badly from factory, and never quit until I changed tire brands and THEN had them road force balanced. Now I have a very silky smooth ride.

[OutKlast]

Originally posted by Dominic:
Have your tires roadforce balanced, not normal balanced - it helps a lot. Then, be sure your alignment is in spec.

Mine vibrated badly from factory, and never quit until I changed tire brands and THEN had them road force balanced. Now I have a very silky smooth ride.

Who does that and what does it normally cost?