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Discussion Starter · #1 ·
Hey everyone,
After pokin' around on the forum for a few years, I decided to join up. Unfortunately, my first post is an issue that recently began.
The car is a 2009 S80 V8 Executive and I've done a few basic mods to it. Lowered it with the B&R springs, upgraded to the Koni adjustable's, and even welded up a basic cat-back exhaust for it.
The car has been great until this point, I'm just shy of 70k miles so far. What I've started to notice is that around 40mph (and just about dead silent until 40) the car starts to make a humming sound, almost like road and tire noise. It seems to just about go away or possibly is just too hard to hear with the road noise around 80~ish. It's really difficult to diagnose it front to rear or even from one side to the other and really there isn't any associated vibration along with it. It's not RPM dependent as going in or out of neutral makes no difference. I've rotated the tires front/back and side to side with minimal affect to the sound, at least none I can hear. From the searching I've done on here and else where, it sounds like the next place to look is the wheel bearings. Has anyone else ever experienced this or had any luck diagnosing this one way or another? Any help is greatly appreciated.

Thanks gents!
 

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My humming sound was traced to cupped/feathered tires which, consistent with Volvo's recommendations, had never been rotated in 24,000 km. The noise first appeared when I rotated them, and after several hundred noisy kilometers I rotated them back to their original position where they are acceptably quiet. If you've already tried that, and can see no other evidence of tread problems, a wheel bearing might be the next most logical place to look.
 

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don67: How do you mean cupped/feathered tires? As in worn unevenly, or... something else? And are you saying the tires should be rotated in a particular way or shouldn't?

Erron S: At 80 MPH I can only guess the noise is being drowned in other noise. Does it start exactly at 40 MPH or is that when it becomes audible?

Putting it in neutral doesn't really make a lot of diagnostic sense to me. Turn off the stereo and fan and run it at what-ever speed the humming is the most noticeable. Put it in manual and try shifting +/- one gear of which gear you're in, at a constant speed, and see if it makes any difference. Does the sound change pitch or volume with speed or RPM, or is it just a humming that's there from 40+ MPH?
 

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Discussion Starter · #4 ·
My humming sound was traced to cupped/feathered tires which, consistent with Volvo's recommendations, had never been rotated in 24,000 km. The noise first appeared when I rotated them, and after several hundred noisy kilometers I rotated them back to their original position where they are acceptably quiet. If you've already tried that, and can see no other evidence of tread problems, a wheel bearing might be the next most logical place to look.
I think there is something to this.

Over the weekend, I checked everything I could get my hands on. Bearings, CV's, brakes (even going so far as to spin up the discs and look for an off balance, dial gauge for warped, etc.) and the rear end. It all felt/sounded/looked great.
Here's the fun part... When I had the tires off, I rubbed my hand around the tires and felt a saw tooth effect to the tread blocks. I had to look pretty close to even see it, but it's there. There's not much but it certainly is present. (1/16" maybe?) I think this may be exactly what is going on as the humming started about the time I rotated the tires front/rear/flipped. I suppose now the question is why are they doing this and I can only assume it's because of the lowering and non-rear camber adjustment. I'm not stranger to wearing down a shoulder of a tire from too much camber but why is it feathering? Toe is in spec from the last alignment so i'm guessing it's simply from the ultra-squishy rubber Volvo uses for the bushings. I may look into that at some point but for now I'll leave it as is with the tires rotated and see what happens.

Thanks for the input gents!!
 
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