Golf VI R :: Harmonic Vibration Started At Around 65 Mph On Wet Pavement

The other day, as I got up to speed on the interstate on moderately wet asphalt, a harmonic vibration started at around 65mph. Felt it in the seat of my pants more than in the steering wheel...the entire chassis was vibrating. So bad that when I called a friend to ask him what he thought, he could hear the vibration in my voice. Clutch in, engaged, under power, under back pressure - nothing affected the pitch or harmonics. Below 65 changed the intensity, but had to slow to 50 to make it stop. Took it all the way to 90, but no difference. This kept up for the entire 70 mile trip.


Now for the weird part. On my way back, 2 hours later, the rain had stopped and the interstate was now dry. No vibration. Just as smooth as glass all the way home. I had it in for service recently, because it happened once before...no codes, no clue from tech as to what brought this on. And just to be sure, I had them balance the wheels...very minor weight adjustment. I called the dealer on the way back to tell them it happened again, and all the tech could suggest was to stop by next time it was raining so they could road test it.

Even more weird is the fact that this has only happened twice and I drive the interstate in the rain all the time.