I have an 07 Is250 awd. It drove and rode perfectly. I lowered it on Fsport springs, no vibration, still rode perefect. They I bought 19's for it....Staggered... But, my tires are equal diameter, 235/35/19 up front, 275/30/19 in the rear. Now while I drive I get his weird vibration, around 65-80mph it feels like the rear tires are out of balance, I had 2 different shops check them and they both said the wheels are balanced right. I do have 73.1-60.1 hubcentriuc rings installed as well. They fit snug on the hubs so I know they are right.

Will an alignment fix this? (It was straight before I installed the springs, and after while the stock wheels were on. Negative camber increased in the rearfrom springs)
Will road force balancing fix this? (They were high speed balanced twice)
Is a U joint going bad?
Is the different width between the front and rear tires creating issues for my AWD?
What about wheel bearings?

 

Are running with a stretched 17 inch tire on a 19 inch wheel in front? Also it doesn't sound like a camber issue because even with 20s on my rears and negative 3degrees camber without alignment (just got coils) mine never feels out of balance in the rear.

Given that mine is RWD though, maybe your awd is is having troubles keeping up with the staggered / heavier wheels in the rear?

Have you switched the wheels back to stocks to see if it feels the same? If you do and it does feel the same it's the tire/wheel configuration.

 

Typo fixed... 19's all around lol... I was wondering if the weight would throw off the awd system. I am switching the wheels back to stock today.
I'm also wondering if the hub centric rings I bought from ebay might be crooked or not perfect. Perhaps $4.00 for a set was too good to be true.

 

Yea I would stay way from the spacers, lol but let us know how the stocks feel once they are back on.

Hopefully someone running staggered awd will see this thread...but I only recall seeing one or two members as of late with that