It's weird because I don't really feel any vibration at all but there's a distinct rotational Wow Wow Wow Wow sound that increases and decreases with speed. If I had to guess which one it is, I'd say the back right but who knows for sure. BTW, It loudness, etc is dependant on the type of road surface. Some roads you can hardly hear it then then I'll hit a patch of flat back top and it's very noticeable. Is this typical of a tire balance problem even though there's no noticeable vibration or is this something worse? Thanks! B.