Whole car vibrates why?!

jamesj1996

Hey guys so yesterday I went to go get my ebrake adjusted because I had new rear rotors put on and it needed to be adjusted it wasn't grabbing on hills. Anyways I was driving home on the freeway going about 80 and noticed that almost my whole car was vibrating I felt it vibrating from under my seat and behind me also the steering wheel was vibrating but was not shaking back-and-forth the tech that worked on my car did admit that it was really busy and he had to get me in and out because he does work on the side for me so therefore he admitted that he did drop the wheel kind a hard really quick by accident and one of the wheel weights might have came off also I have 20 mm spacers in the front and 25 mm in the back both bolt one by h&r. he said that it could be the wheel spacers but this never happen until I drove home last night ever since I got the spacers installed I had no problems until yesterday so I doubt it's the spacers but she said that a wheel weight might've fallen off causing the wheel to be unbalanced which causes the vibration I will have to wait until Friday being that it's snowing here and they are closed on Thanksgiving but what do you guys think could be the issue

*obviously he will not charge me to fix it if it is the wheel weights anyways he does work for me on the side I don't go through the dealer but it is a Nissan dealer and it only happens when going above 80 miles an hour I checked for nails in my tire and flat but there was nothing