Are you sure it's the tires?
Drive train problems, particularly driveshaft related ones, also sound like that. Inspect the tailshaft of your tranny, and pinion of your differenntial for signs of leakage. Drivetrain vibrations often cause fluid to weep past the seals from the vibration.
Front wheel bearings can also sound like that as well.
Not at all sure from the information presented what it is -- I'm just throwing out some other things to consider and to examine.