Alfa 75 3.0 V6 QV wheel vibrations

[furanko]

Dear all

I have owned a genuine 75 3.0 V6 QV for two years which had only 35000 kms on the clock when I bought it and I covered just over 3000 since. There were some minor maintenance works to carry out this year but I truly am very lucky.

There is one thing that I (we) have not managed to sort out which are the vibrations transmitted to the steering wheel. The car has the original optional 15" alloys and when I bought the car Michelin winter tires were fitted. There were some minor vibrations but nothing worth worrying about - I thought at least.

At the beginning of 2009 I replaced the winter tires for a set of Turkey produced Pirelli P7 (for originality purposes). Fitting the tires was quite a difficult task as balancing the wheels turned out to be a nightmare. I opted for glued balancing weights to improve the looks.

I now have much stronger vibrations which are not only annoying but certainly strong enough to make all bolts go loose with the time. We have tried to turn the tire on the rim, balancing the wheels on different machines, etc. but with not much effect.

It seems that the vibrations tend to reduce when I drive longer distances (maybe from 10 miles onwards). The vibrations are particularly intense at speeds between 110 and 140 km/h (70 to 85 mph) but also seem to vary. But I have also found out that apparently 1. it isn't such a good thing to glue the balancing weights on the rim instead of using the traditional form on the rim flange, and, 2. cheaper Pirelli tires seem to have quite important levels of unbalance.

Has anybody had similar experiences and would know what the solution could be?

Thanks all from Switerland!