i have this weird shaking on the freeway around 75+mph, i can see my passanger side seat shaking.. it seem like it coming from the rear. im lower on espering spring(or however u spell it) with T1R race version spacer.

 

95% chance that your wheels are out of balance. I developed the same thing and would have bet money that it wasn't the wheels because they were balanced only a few weeks before it started... turns out that the stick-on weights had somehow removed themselves from my driver-side rear.

 

i had same problem, and thought i needed to balance my tires, after closer examination, turned out i just needed new tires my rears were completely shot, got new tires, problem solved

 

thx guys imma go try to get it balanced