Wondering if anyone had this or could know/guess what the problem is... When I drive at about 40mph, gets a bit louder after the car has warmed up a little, I always seem to get a quiet low frequency rumbling sound as soon as I come off the throttle and it stays there until I begin to accelerate or brake with some force. Slight changes in speed do not affect it much (pitch does not change). I have noticed this happening for a few months now and it does not seem to affect handling in any way. Ideas so far: 1. tyre noise - slight reduction after switching rubber from a different car, but still there 2. wheel spacer - haven't tried to remove this and check if the sound is gone (on my list of things to try) 3. wheel bearing - jacked the car up and spun it, with no problems found 4. CV joint - not sure about this as I never had a CV joint go on me yet and not sure of the type of noise this makes 5. tracking out??? not sure about this as it's not pulling Anyone have other thoughts/ides that I can try?