strange hum at 30mph

[4point2]

Hey guys,

Maybe someone can help. I just picked up my Avant last week and within a couple days a hum has appeared. Well actually there are a couple. The first one seems to appear at around 30mph and kind of disappears at about 45, it's still there but faint all the way to about 75 where wind noise takes over. It seems to not vary regardless of left or right turns, and occurs whether on the throttle or not which points to drive train, correct? Thing is it gets quieter if I apply the brakes slightly. Any ideas?

Second noise occurs as I slow down to a stop. It's a really loud hum almost vibrates from 25 down to about 10. I'll try to grab a video in the morning and post it up.

Any suggestions welcomed.

Thanks

Alex

[thomasskull666]

Is it entirely dependant on speed or can you tell if there is a certain RPM range that produces the noise? That will help isolate the problem.

[LJH]

does the car have slotted or drilled rotors? Maybe tires? Might be a wheel bearing but the fact that it does not change when you turn makes that less likely.

Cheers,
Jim

[4point2]

tried getting a video but I couldn't get anything but rattles and wind / road noise. Rotors are the stock ventilated style. It seems to only happen around 30 ish, I'll try with a different gear selected to see if it's rpm vs road speed. Seemed to be less this morning on cold start was definitely worse this afternoon as i was getting near home.

[useridnotvalid]

Might be time for a wheel alignment and balance. Have you hit any big bums lately or driven on some bad roads

Sent from my Samsung Galaxy Note 3

[Brettannica]

This might be a silly question;
It’s not the straight cut gears you are hearing that power the A/C and P/S.
They can make a bit of a noise dependant on speed and had me puzzled when I first bought my car.

[Quadfreak]

My first thought is wheel bearings...but I don't know how much of an issue they are on this platform. I know on my B5 I was replacing the rear wheel bearings almost every 6 months. But those would get loud fast and and change tone with wheel speed. Making it easy to pinpoint what side it was coming from.