When I had my LC maintenanced, I also told them to check on the humming sound coming from the rear section above 65MPH. i was afraid it could be the third member. They did the road test and based on the road test, it was coming from the tires that are coped inward. Best thing to do is replace the tires. I have bridgestone Dueler and it is not worn, so I am thinking of keeping it until the next time I will replace my tires. I do not think it is worth changing tires for a little hum. I have read lots of posts regarding the humming sound from various users. Check your tires carefully before getting in too deep with othe rexpensive area. I am considering replacing with either Yokohama, Cooper, or Kumho tires in the near(I hope) future.