The tyres are of the same make, and dimension all around for all my wheelsets.
I have tried:
2 sets of 205/55-16 wintertyre (Michelin & Continental)
1 set of 215/45-17 wintertyre (Pirelli)
1 set of 215/45-17 summertyre (Dunlop)
1 set of 225/40-18 summertyre (Dunlop)
Pressure and balance should not be a problem. I've varied the pressure a little, just to see if that's make a differ. I can't say i felt any difference on the vibes. Handlig however, seems to be very affected by the pressure.
Just to be sure, I've sent a set of tyres to be rebalanced today.
I mentioned that I had my gearbox changed. The old one made an awful rumbling noise on the 6'th, from approximately 80km/h to 120km/h. The new one is still not perfect, but a lot better. This rumbling noise and vibration however, differ quite a lot from the vibes comming when I'm accelerating when the car is heavy.
Rgds,
LavaIS