240 DL sedan B230F 1989, 243K kilometers, well maintained car

Hi all,

Last year I bought used a set of virgos. I installed (new) Predator 'performance tires' (REALLY crappy tires by the way), 205/60R15

I was noticing throughout the summer that the car would often go into a vibration at fast highway speeds (over 140 km/h). I often atributated this to some misalignment in the steering, and occasionally tweeked it and it helped but still...

Now I put back my steel rims with winter tires 195/70R14. The car glides completely effortlessly and vibrationless at 160 km/h highway. No I don't normally drive fast at all just wanted to try it out.

So my question: Should I assume the virgos and summer tires and misbalanced? Note that when I bought them I asked the guy to verify that the wheels were not bent, he said they looked fine. I know virgos bend easily.

Should I get them re-balanced in the spring?

Would the slight difference in overall wheel/tire diameter require a re-alignement to fit the virgos and summers? I thought not at the time...

Thanks,
Greg Mustang
Montreal - Ottawa
Canada