when the car had my sommjertyres 18' on, I have a vibration from the fron from 55 mph getting stronger towards 80 mph. The I changed to my 16' wintertyres, perfectly balanced, Still vibrations, but not so strong, but now I can also feel it in my seat, which indicates vibrations from the rear, what could cause these vibrations?

 

I had a similar issue.

Things to check:

Alignment.
Wheels out of true (slightly bent).
Wheels/tires out of balance (I see you say they are perfectly balanced, but......)
Tires out of round (uneven tread, bulges, etc....)
Loose lug nut or two floating around somewhere.

Could also be something in your ball joints or in your suspension, but rather unlikely as when you changed the wheels out, the vibration subsided.

I had the same issue and it turned out to be the tires were worn and my rims are slightly bent (I live on a dirt road and it is tough on the rims). Replacing the tires and getting an alignment solved 90% of the issue.

Until I move though, I don't really see the point in "re-true-ing" the rims, or replacing them. (Shops can machine them perfectly back into shape.....)

 

byrnel, if the steering wheel is wobbling back and forth when you are driving 55-80 mph, then this is your front end alignment being off just slightly. Now, it may be that one of your summer tires is also slightly bent, which is making it worse. But, at the same time, if your summer tires are wider, that will also affect how bad the wobble is too.

 

I had an issue with a rubbing sound and vibration... had the car checked and rechecked... alignment done 2X. I decided to change 2 tires (they were close) and that cleared up the sound and vibration.