Humming/droning sound - don't think wheel bearings

[Mizen]

Hi,

I have an annoying low droning sound that seems to be coming from the rear of the car. It is linked to roadspeed not engine speed, and raises in pitch with speed, but then beyond 40mph seems to stay at the same level.

Everything you read about suggests rear wheel bearings, but there is absolutely no difference at all when cornering, and **** knows i've tried - so unless wear is completely equal on both sides, i'm not convinced.

Got the car up tonight and removed both wheels (not the caliper and pads -was too dark, and getting too late!) - both feel like they need the same resistance to push, neither make a grinding sound at all, neither have play. I was surprised at how the discs didn't spin freely, and there was noticeable resistance between the disc and pad however (not a mechanic - is that normal? seems unnecessary friction for the car to get past!)

My thoughts are either:

1. Front wheel bearings, as yet not checked (doubt it - as sounds comes from rear, and doesn't change when i load left or right by swerving)

2. Rear wheel bearings. Both equally worn (but as both feel the same when spun, difficult to conclude that)

3. Heat shield above exhaust is all over the place, and needs to be put back with larger washers. Could it be resonating? (seems a long shot)

4. Exhaust mounts perished (make exhaust sit unevenly but shouldn't make noise?)

5. Inner wheel arch lining is flapping (but nowhere near the wheel - just an inch down).


Any ideas or similar experiences?

Cheers,

 

[Saint27]

Hi, i had the same issue. I had both rear brake discs replaced (which include the bearings) which the guy appeared to over torque causing the bearing to fail. I had both replaced under warranty and all seems well now. Hope this helps.

 

[Miller]

If its not the bearings, check your tyres for stepping as makes the same noise

 

[mattd1984]

Are the wheels hot after driving?

 

[Mizen]

Rears aren't - not checked the fronts though, but will check tonight. Sound definitely feels like it originates from the back, but I know sound resonance can do funny things, so could still be the fronts..

Best guess so far is both rear discs, we shall see!

 

[Mizenfb]

Hubs don't move when shaken or grind when rotated, wheels don't get hot, doesnt make sound on either side vs. the other and tyre wear is even!! Proper mystery is this...

 

[Carbon Chaos]

Jack up the rear a side at a time and put a block under the fronts so you can release the h/brake then spin the wheel by hand and hold on to an accessible part of the suspension that side,feel for roughness when rotated.

This is the best way of testing for failed wheel bearings as in an M.O.T

 

[Mizen]

Turns out if it looks like wheel bearings, sounds like wheel bearings, smells like wheel bearings - it's probably wheel bearings.

Gave up trying to work it out so took it friendly local MOT/Tyre/Exhaust place. Chap is 100% confident it's rear bearings, and getting new pads + discs fully fitted for £252 today. Considering i'd be struggling to get the parts for less than £150 myself plus the hassle of fitting, getting it done today whilst at work is a no brainer. Chap reckons if they're only starting to go on the way out you'll struggle to spin the discs fast enough yourself to detect it, but there is nothing else that sound can be.

Off to BG Motorsport on Friday for a refurb, and hopefully new PMS top mounts and brace if it arrived in time, slowly getting this thing back to former glories..

 

[Mizen]

Confirmed issue is solved, and was rear discs as suggested by one of the first responders.

FWIW - the usual tests you can read on the forums don't always work if damage to bearings is light. There was no noticeable difference in wheel temp, they didn't spin grouchily with the wheel off, the discs didn't move when shaken, and the noise didn't change when loading one wheel or the other.