Driveline vibration!!! I need help!

How do you know the balance on the tires are ok? I bought a new set from a tire dealer.. had a rear vibration at 62 that WOULD NOT GO AWAY. They replaced one of the new tires, they balanced them 4 times... no fix.

Just out of curiousity, I took it to another tire place (new place) and they balanced them. Smooth as silk. Make sure you don't have a bad belt in a tire also.