Hey, lets dont be knocking the Metzlers.......lol. I have ridden them for 63000 miles so far, they make a humming noise at slower speeds, more so as they age, less with lower tire pressure. But to me its a hum, a noise not so much a vibration I feel, as the sipes edge out I think it is more pronounced. Cupping makes it louder.......got a new set waiting to go on......soon.
As one of the guys adding to this Metzler theory...I'm not "knocking" the tire. It just FREAKED ME OUT right after I put new Metzlers on the front and back and I got a new slight decel vibration at 30ish MPH! Just glad to hear other people can support my hypothesis.