Wheel hum

[x-dog83]

Just replaced my front AND rear wheel bearings about a week ago. Due for an alignment soon.

MY PROBLEM: I am experiencing a low frequency hum at speeds between 25-45 mph. Sometimes it's constant and sometimes it "warbles".

I had a buddy drive down the road past me and didnt hear anything abnormal from outside the vehicle as he passe by, and the wheels dont seem to wiggle while in motion. The sound seems to be just inside the vehicle, under my feet.

Could this be due to the alignment being off? Or could this be a balancing issue? Or is this just the nature of huge tires? It's pretty loud, i can hear and feel it over my modified 4.0-6cylinder engine when im reved up to 4..


91 explorer sport
5.5" lift
33" rubber
Locked front and back
Geared 4.56

 

[Anime]

Hard to say. Could be a lot of things, from regular tire/road noise to just pooly balanced wheels/tires, or even an irregular wear pattern on the tread that hums differently depending on the pavement surface.

If you raise up the wheels/tires and check the wheel bearings/ball joints and everything is tight with no wobble, and the rest of the drivetrain (driveshaft, u-joints, differentials, including fluid, etc.) is good, you should probably have the wheel/tire combo balance checked. Often an unbalanced tire, especially a larger, heavier one, will give that hum that warbles.

There's a chance it could be fixed with an alignment as well, but that would be a pretty serious correction. If it aligns fine, and no issues are found otherwise, you could just have noisy tires. Keep in mind some tires just wear funny, or cup and make noise, too, so it might be something you have to get used to until the next set of tires.

 

[Naasau]

Out of curiosity, what 33" tires do you have? and how old/what pressure are they at?

 

[x-dog83]

I bought the vehicle a month ago and it came with

33x13.5r15 superswampers (rear)
33x12.5r15 pro comp-xtreme (front)
Both with about 80% tread left on them.

I plan on changing the tires in the next few months to all Runway Enduro M/T's.

 

[x-dog83]

P.S.
They're both rated at 35psi max and I have them at 30psi.

 

[Anime]

Mud tires in general and super swampers in particular are well known for their loud hum on the pavement, just how they are. They also don't always balance all that well.

You could be getting additional noise due to the different tread patterns front and rear, which might be combining to make a certain annoying frequency or two that gives whatever noise you're hearing.

It'd definitely be a good idea to get all 4 treads of the same type and size if you plan on using 4WD, having tires with different diameters when all 4 wheels are being driven is a no-no.

 

[x-dog83]

Yeah, I agree with your statement on the tread matching. It's DEFINITELY a good idea, and the reason why I want to change them out ASAP.
The previous owner (ironically) was a member of this forum, as I found out after I bought it at a local used dealership. Googling the specs of my rig and happening upon a pic of her, it took me here and I got to read all his posts over the years. Kind of fascinating really.
WAExplorer was his name.
Anywho.. I dont know what he was thinking with 2 different tread types on the wheels seeing as how he seems to have done all the custom work himself and should have known better... Time to save up some paychecks!

 

[Naasau]

I know the feeling. Since you're aiming at new shoes, I would wait on the alignment till you get em.

I agree with Anime that the two different tread patterns are probably causing some freaky harmonic resonance thing. My wife's Heep has M/T's and even though they are all the same and at proper pressure, god forbid you go more thaqn 5k miles between rebalancing them. The oscillating drone that they start giving off can be maddening... and they're only 31".