What was found
PHX - AFTER TAKEOFF AND DURING GEAR RETRACTION, CREW REPORTED VIBRATION FROM THE NOSE LANDING GEAR AND HEARD A NOSE WHEEL BEARING GRINDING NOISE. NOISE CEASED AFTER GEAR RETRACTION. AFTER SPEAKING WITH MAINTENANCE, IT WAS DECIDED TO RETURN TO PHX. CREW DECLARED AN EMERGENCY AND RETURNED TO FIELD AT PHX. FLIGHT LANDED WITHOUT INCIDENT AND TAXIED TO THE GATE. MAINTENANCE REMOVED AND REPLACED BOTH NOSE LANDING GEAR TIRES FOR BEING OUT OF ROUND. AIRCRAFT OK FOR SERVICE.