Humming noise... new tires or wheel bearing.

[4greenfords]

I had a pair of Cooper Discoverer ATR's put on the rear of my wife's Explorer this weekend and since install there has been a consistent humming noise coming from the rear of the vehicle. The front tires are the same make, model, size and are a few months old (less than 3k miles). The front of the truck is quiet but there is a consistent humming coming from the rear end, it rises and falls with speed.

I read up on the rear wheel bearings and also have heard new tires with a deep tread pattern can have some decent road noise, looking for opinions or suggestions in diagnosing the problem. I don't want a bad bearing to ruin new tires.
What are your thoughts opinions or suggestions in determining detween the two?

Thanks in advance.
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'02 Explorer XLT 4.0L V6 4WD - Bone Stock

 

[03Mach1]

Sounds kind of simplistic but since the tires in the front do not produce any noise but the ones in the rear do, I would switch them around and see if the noise stays in ther rear or moves to the front.

I realize they are the same model and size but you never know. Its worth a shot before you start buying and replacing bearings.

 

[imp]

Easier yet, try 2 drastically different levels of air pressure in the rears.....

maybe 20psi, see if noise level changes, then maybe 40, same test. If noise level is not noticeably different, look for possibility of noise not being tire-generated.

Just a thought. imp

 

[4greenfords]

Thanks for the suggestions guys. I'll start by dropping the pressure and test driving it, listening for change in sound. If no difference I'll swap the fronts and rears and check again.

I hate working on cars in upstate NY winter.... :

 

[justin_b31]

AT tires do make a lot of road noise. because the rear compartment is very close (with little insulation between the outside and inside) the sound does transmit well inside so it makes for a difficult diagnosis.

Other than the sound being very loud at 25-30 mph there were no other indications of bad bearings.

But then a year later the noise changed, it sounded like I ran over rumble strips. Not quite as loud or continuous, but noticable the same for me.

A tell tale sign is a leaky differential on the 'bad side'. Bad bearings mean the wheel wobbles, wobbling bearing makes the CV axle wiggle back and forth, which allows gear oil to leak from the diff.

Parts are difficult to find in that it is not generally seen as a 'replaceable' part and the bearings were updated. Easy to remove the knuckle and have a shop press em out and put new bearings in.

additionally, the diff seal was updated too with a different part number.