I have a 2000 chevy cav. I recently noticed a low rumbling noise as my car is in motion it increases as the car speeds up. Acceleration doesnt seem to effect it sound maintains same pitch while coasting. Already replaces brake pads wheel bearings and rotors. Had tires balanced and inspected. It almost sounds like I have a flat but i dont. Lug nuts are tightenex to spec. Could it be the caliper?

 

Does it pull to one side when braking?