Hum between 70 & 80 MPH - Is it normal?

[consultant1027]

I bought a used G37x Sedan. My first RWD (essentially RWD biased AWD) car. Like all different cars I'm getting use to the noises. It actually has virtually no strange noises. Pretty quiet on the highway. It doesn't have stock tires, brand new tires, off brands I'm not familiar with. I just drove it 700 miles. I noticed that between 70 and 80, most pronounce at about 75, there is a humming noise that is coming from the rear with a slight oscillation sound to it. Like the noise a wheel or tire might make that was just a tiny bit out of balance maybe. But it is so subtle, I guarantee that 95% of people that rode in this car would think I was crazy as it is *barely* noticeable and totally unoticeable on pavement that isn't very smooth (like new asphalt). I'm wondering if it is just the rear part of the drivetrain just reaching some sort of harmonic oscillation point with the car or if it may just be the tires or an out of balance wheel. There no vibration at all that I can feel. I suppose since the brand of tires on the front is different from the rear I can rotate front to back to at least eliminate the wheel/tire cause.

But I'm also wondering if it is just a 'normal' noise and it is just that I'm not used to it since I just got this car? Based on prior experience with dealer service depts I can say 99% that the dealer would not be able to diagnose it as in my experience very subtle things they just disregard and say they didn't notice anything wrong. You have to wait for it to get worse before they 'notice' it and do anything about it.

[kmckis1029]

yeah im like you and i notice every little noise... i have stock tires and cant wait to get rid of them! So with that said my first guess would be the tires...

[telcoman]

yeah im like you and i notice every little noise... i have stock tires and cant wait to get rid of them! So with that said my first guess would be the tires...

+1
Tires
Crank up the stereo and you won't hear the noise

Telcoman

[Poyzinous]

cheapo tires can cause problems. What are they?