Running my 2013 CMSAll4 in on Thursday for a checkup. No real problems to speak of. It's due for it's first service, but I noticed some loud noise seeming to come from the rear of the car undercarriage. The road I was on wasn't the smoothest, but it wasn't really bumpy and rough either. It wasn't during construction or anything like that... just an average paved road. It just seemed like it got louder and more noticeable when I did go over small bumps or dips. It almost sounded a wheel was loose or a tire was really low on air... like a grinding. But there was no change in the handling or drive.

I turned off that road and parked the car in front of the restaurant we were going to. When we left, I had to go another direction to her place, so I listened for it but couldn't duplicate it again. I haven't heard it since. I typically have the music up and going, so I never really noticed any real road noise before. In this instance, I was in the car with my g/f and the radio was down so we could talk. I do have the factory runflats on there. I've never hit any big bumps or potholes or really been off-road in it at all so I didn't think it could be anything with a control arm or joint? (i'm not sure if that's the correct terminology). I also cleaned out my car completely in case something was rattling around but no luck finding anything that would've been rolling around making the noise.

Is there a chance that the runflats are really THAT noisy on certain roads? I only have 10,000 miles on them so there's plenty of tread... The best way to describe the noise is almost like the sound it makes when you are driving on the highway during construction over the roads that have been stripped and you can see all of the little lines it it. You can hear the noticeable change in tire sound.

Anyone else have some really significant noise from their runflats?

 

Check that the cover on the positive terminal of the battery hasn't unclipped and popped up... Mine did and it sounded a bit like your description in all respects other than location ( sometimes your mind can be tricked by the direction a sound is coming from)

 

I have a rattle that kicks in around 40 and up, smooth road or otherwise. I discovered that the plastic guard underneath the car on the drivers side is damaged and my rattle is from it bumping up against the car due.