i lowered my car and put 18" wheels/tires on it about 5 months ago. everything was goin great, a little more noise from the low/pro tires but i could definately handle that. the last few days though i've been hearing this louder, annoying like humming noise that seems to be coming from the back of the car. in the cabin with the windows up as u gain speed it gets louder. at 35-40mph the car starts to rattle a little bit until i hit 45mph but the noise is still there and stays loud past that speed. doesn't sound like a grinding noise or like a rubbing noise, can't really explain it. had the wheels/tires rebalanced and it's still making the same noise. i also checked all four tires to see if they're rubbing anywhere and found nothing. just wanted to ask you guys in case you've experienced the same thing or in case you know what it could be. it's annoying the hell out of me. i'd appreciate all your inputs on this issue. thanks in advance

 

Sounds like one of the belts in your tires have separated. Thats what causes the hum.

If you run your hands across the tire tread you MIGHT be able to feel irregularities.

Time for a new tire. Hope you have a warranty.