I have read through old posts and didn't find a solution. I have the bonnebeast in my sig and at about 60-65 the vibrating starts and then at about 75 -80 is isn't as bad. I just got this car and don't really know much about cars but I did buy a Hayne'* book to help me and nothing on this subject. The ride is perfectly smooth if I'm driving through town or something but if I hit the highway then you have free vibrating seats . I read a post from '05 where the guy replaced almost the entire front end, changed tires, and wheels but still nothing. Anyone know what this problem could be?

Start with the basics like a wheel balance and a tire alignment. Check for bent rims or anything out of the ordinary.

rotors will do this also. So will a tire that has belts that slip.

If your seat backs are vibrating it most likely in the rear wheels.
Floor by the gas pedal - front wheels.

I have had mud caked onto the inside of my rims(long story) made my car shake like a belly dancer.

Well it'* not just front or back it'* both. MY whole seat vibrates and back seats are the same. The steering wheel, hood, floor, everything vibrates. It is perfectly fine driving around town but if you get on the highway it'* not fun anymore :( I just washed my car so I know it'* not mud in the wheels and the wheels don't look bent and can't see any abnormal tire wear.

did you look on the inside of your rims? if they are clean, are you missing any weights from having your tires ballanced? I hope we can help you figure this out, I hate to see a misserable bonnie

The wheels don't appear to have ever been balanced because I can't see any weights. any idea how much it will cost to have them balanced and/or aligned ? I live near new philadelphia if that helps with figuring cost

I had a similar problem, although it seems mine was less intense than yours. Had a vibration at certain speeds. Figured it was a tire balance issure. Took the car in for an alignment and it could not be aligned since the pass. side front wheel bearing was worn. With the front tire off the ground you could grab the wheel (tire) and move it around. Seems like it would only wobble around maybe .040 / .050 inches, but after I replaced the bearing (took about 1 hour) all the vibration is gone...

I am sure the driver'* side will be next - 190K on the original bearings is not bad!

usually a wheel bearing will make a low howling or grinding noise and you will hear it most when you are making a turn while moving(going around a shap curve) if you steer left and the sound stops, then its your left wheel bearing if you turn right and it stops, check the right bearing. I have replaced both of mine in the past year.