My 2001 XC70 rather suddenly developed a noise which appears to be coming from the right rear wheel well area. It's easy to describe. Imagine you put the knobbiest snow tire in the world on that one wheel. The loud hum is directly related to wheel RPM. It starts to manifest itself around 28-32 MPH and increases in volume and pitch as the cars speed increases. Putting the transmission in neutral at highway speed does nothing to decrease the sound, hence rulling out engine, ehaust or transmission. The really odd thing is that if I open the window I don't hear the sound from outside the car. The only time the sound deminishes is when I take a right hand turn at speed. The Goodyear tires have on the car were very quiet until this sound suddenly appeared. They have only 20K miles on them and show no unusual wear and are free of any forign objects that would cause the sound. The car track fine under power and breaking. I have a service appointment in a two days and wondered if any of you had any thoughts.

 

One of 2 things will cause the noise.
1. A bad tire or feathered tire.
2. A bad wheel bearing.