Strange noise when turning

[MiniGeek]

I have a 2005 Cooper with 25,000 miles on it. This past weekend I noticed a strange noise when I was turning to pull into my driveway. When I first heard it I thought it was a warped rotor because the sound would oscillate based on the speed that I was going, and sounded almost like a grinding sound. Tonight I had my wife drive the car really slowly around our driveway while I stood outside the car. From outside it sounds completely different than it did when I was in the car. It is more like a rubber squeaking sound. It sort of sounds like someone walking with one shoe that squeaks.

The noise is coming from the right front wheel and it doesn't matter which direction the car is turning. I noticed that there is a rubber boot at the end of the axle where it attaches to the wheel assembly, and that appears to be where the noise is coming from.

Has anyone else had this problem? Could it be the rubber boot that is causing the noise, or is it the joint that the boot protects? It has been a lot colder here (Portland, OR) the past week, so I'm wondering if the rubber boot has become more rigid with the sub-freezing weather.

[MiniGeek]

The strange noise turned out to be my tire. I have the Goodyear run-flat tires that came on the car. The right front tire was about 5 pounds low. After inflating the tire to 35psi the noise is gone.