One way to know if your car needs new wheels is by checking for significant play in the bearing. You can do this by rotating the wheel in different directions and noting how much play there is. If there is significant play, one or more bearings are bad and need to replace soon.
Another way to check for bearing significance is by rotating the wheel while applying pressure to one side of the hub. If the wheel moves significantly, it likely indicates that your bearings are bad and need replacement. Always consult with a mechanic before making any repairs.