What was found
(CAN) PILOT REPORT THAT SHORTLY AFTER TAKEOFF THEY EXPERIENCED A VIBRATION. THEY COMPLETED CCT & RETURNED TO AN A.M.O. FACILITY. NOSE OF A/C WAS RAISED & NOSE WHEEL WAS MANUAL SPUN. MAINT FOUND NOSE WHEEL BEARING WAS NOT CORRECTLY PRELOADED CAUSING TIRE TO SPIN CONTINUOUSLY. IT WAS ALSO NOTED THAT TIRE WAS ABNORMALLY OUT OF ROUND & THAT ONCE WHEEL STOPPED SPINNING A TUMBLING SOUND WAS HEARD FROM WITHIN TIRE ASSY. WHEEL WAS REMOVED & DISASSEMBLED. FACTORY BALANCE W8 (1.83 OZ.) FOUND DETACHED & FREE TO FLOAT WITHIN TIRE ASSY CAUSING AN IMBALANCE CONDITION ON NOSE GEAR. WHEEL ASSY WAS REPLACED & A/C WAS RT-SRV.