new rotors = shaking car?

[Beaker]

Okay, here's my problem.
I put on new rear rotors, (powerslot) and new EBC greenstuff pads all around, now I have a very bad shake/vibration coming from the rear of the car. If I'm tooling around in town at 20-25mph it feels almost like the rear wheels are rolling over small speed bumps. This goes away usually by 35mph, then turns into a nasty vibration at around 70mph, and by 75 the whole car is rattling so bad I have to slow down below 65 before it goes away.

Here's what I've checked so far.
I can't see where any wheel weights have come off.
The wheels sit on the hubs straight.
No dragging pads, all wheels spin freely when the car is on jackstands. No pulsing in the brake pedal.
The new rotors appear to spin perfectly round, and are sitting on the hubs flat and even all around.
When on jackstands and running in gear, the rear wheels appear to hop. The tires are on the rims straight, with no noticeable bulges. They seem to "hop" in unison. Just the rear wheels.
Why?

Does anyone have any more ideas before I take it to get the wheel balance checked at the shop?

Thanks

 

[HotSauce GS N/T]

Did you have any shake before you put the new rotors on?? Its not too common but sometimes rotors are manufactured unbalanced. Also check again to see if the rotors are laying flat against the hub. Also, if you haven't yet checked your rear lower ball joints and rear upper control arm bushings do so because both 2g dsms I have had blew the upper control arm bushings right out and caused havoc on the freeway. The piece that connects the hub to the control arm will shake uncontrollably in the control arm.

 

[Beaker]

No, I didn't have any real problems before I "fixed" it. I had a vibration under braking because the old rotors were warped and worn down thinner than spec, hence the new rotors.


I didn't notice any issues with my control arms before, but I'll check it out.

The piece that connects the hub to the control arm will shake uncontrollably in the control arm.

Heh, thus making it an uncontrol arm

Thanks