Greetings all.
I have a rather strange noise that I'm trying to diagnose. It sounds like a loud muffler, or maybe like when there's a truck going down the road with those really big mud-slinging tires on. You know...the sound really big truck tires make? The nobby tires? Anyway, the sound has nothing to do with the engine or muffler, and does not change in relation to the road surface type. I've even brought the car up to speed, shifted into neutral, and turned off the engine and it still persists. The tires are less than a year old, and the brake pads, rotors, and calipers are also new within the last three years. The noise seems to change harmonics as the speed picks up, which is why I think it has something to do with the wheels.

It's very strange...and maddening!
Thanks in advance for the help.

 

Right off the top my head, I would look at the wheel hub bearings starting with the front ones first because they are the ones that are under the most dynamic stress ie. turning, braking, acceleration forces .

 

X2 for bad wheel bearing.

 

It could be the tires as you described. I've heard street tires on cars make some horrendous noise. How does the tread wear look? Is it even all the way across?

Also check the camber on your rear tires. Are they tilted inward at the top? My 2005 were so tilted inward I bought adjustable rear upper control arms.