[TeeGeeThree]

My 2007 E91 has some noise in sync with the wheels/overall car speed - ie, not the engine rpms. It seems to be coming from either the rear or middle of the car. It's a vibration type sound that at high speed is basically a solid noise, higher pitched, then as it gets to lower speeds the pitch lowers and you can start to differentiate that it's a rythmic type sound.

It's not super loud - doesn't feel like an emergency situation - but it just sounds like something is going wrong somewhere.

My first thoughts are things like wheel bearings (although we already had those replaced once), rear tire(s) that need balancing (new tires got put on the car not that long ago), or... that's about the extent of my guesses.

I know without a sample of the noise these will be just wild guesses. But... any wild guesses? What kinds of things are likely to cause noise like this?

Also, any suggestions on how I go about properly diagnosing it?

Thanks ahead of time for your thoughts!

[Groganrocket]

Alignment?

[tlow98]

Center support bearing
Wheel bearings - does it change while cornering?
Old tires
Alignment
Diff bushings, actually just inspect all bushings in the suspension bushings

[marvinstockman]

Feel tires for funny wear patterns.

[dmatre]

If you have a friend with an E90, I'd swap tires first - as tires (either worn or just loud due to tread design) are the most common source of highway road noise.

Typically, big/blocky tread patterns tend to be loudest. However, on the wife's car, we had a set of Michelin Pilot Sport A/S 3+ tires which got so loud after 30k miles that it was unbearable to drive. We swapped the tires with good tread left just to be rid of the noise.

[jsunma]

I'm interested in seeing what you all come up with here as like the OP, I am experiencing this in my E91 and am trying to figure this out without firing the whole parts cannon at it.

In my case, I can say that I have:

1) Replaced rear - and front - wheel bearings with no real change.

2) It happens with both my winter and summer tires/wheels (so it's not tire related).

3) I've replaced rear brakes and rotors (they needed it anyway). No change.

4) Replaced differential oil. No real change.

In my case, the noise is a bit worse when turning (gradually) left. Which is why my very first assumption was that it was a right-side wheel bearing, but since those have been replaced, that's not it.

I can say that there's really not much of a vibration, but more of just a thrumming/grinding noise. I've suspected both the guibo and the center driveshaft bearing, or even a U-joint...but the lack of vibration makes me question that diagnosis. (and again, I'm trying to figure it out before just yanking more stuff off and replacing it)

I have also thought about alignment (one of the suggestions above), but again, the car is not really vibrating or pulling to one side or another. Just noisy.

Last thing I'll add is that it's not entirely clear just where the noise is coming from since it only happens when the car is moving. I've always felt that it was from the rear (center of the car back), but I could be wrong. I don't have a lift to get the car up in the air while running (and accelerating) to check it that way. (although taking it somewhere to get that done might be a good next step)

OH, OP, is your car RWD or xDrive? Mine is RWD.

Thanks for any additional ideas...