stratman

Hi all,

I've noticed a humming sound while driving between 55 and 70 mph. It is most pronounced at about 65 mph but seems to diminish after about 70 mph. I'm running PSS 245/40/18 and 265/35/18 sizes on the stock rims. The tires have about 5k on them. Has anyone else noticed that this particular brand does this or might there be some other issue? I checked the pulleys, tires (plenty of tread left) and front end for looseness, etc. Everything seems in order. I'm hoping it's not the drive shaft or bearing between the two parts though there is no vibration at this point. Anyway, your insights will be greatly appreciated.

Alex.currie44

First question is did it do this before you installed these tires or has it gradually come one since? If it is related to these tires then try to confirm.
Do you have access to a different set of tires and wheels you could bolt on? If it changes then it is tires. If not then you could have a bearing going either in a wheel or in the drive train.
Live with it until it becomes more dominant then re-examine the situation. A wheel bearing or drive train bearing will not fail instantaneously so you won't get stranded.

stratman

Thanks for your reply Alex.currie44. Unfortunately I don't have another set of wheels/tires but I do remember that when the original Continental tires were worn it definitely sounded like the "whomp, whomp" of a bad bearing. I'm kind of thinking that it may have to do with the type of road but, like you suggested, I'll just live with it (it's not horrible by any means) and if it gets worse I'll have the car checked out by my MB dealership. After all, it's still under warranty.

looney100

The fact that it only occurs during a specific speed range makes me think it's a bad balance.

Alex.currie44

Could be that too but a bearing in the drive train can sound the same.

JimmyR

I suspect this will be feathered tires. Always a problem with the stock alignment set up on the C63, but much more likely as you are running slightly oversized tires.
Run your hand/fingers along the inner tread blocks in the direction of tire rotation - you will feel little ridges on the back of the tread blocks - just like the feathered flights of an arrow. Run your fingers the other direction and will feel smooth in comparison.
I reckon 5000 miles on the fronts would be about the time this would show up. You might be able to quieten it down by swapping the front wheels over and/or just put up with it until you need new front tires.