AN EMBRAER 145 AFTER TKOF WAS UNABLE TO RETRACT THE NOSE LNDG GEAR. NOSE GEAR TIRE AND WHEEL ASSEMBLIES WERE REPLACED PRIOR TO FLT.

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ON MAR/XB/99; PLT NOTED ON TKOF; LNDG GEAR WOULD NOT RETRACT. ACFT SUCCESSFULLY LANDED WITHOUT INCIDENT. ON MAR/XA/99; A MECH AND I CHANGED THE NOSE TIRES ON THIS PARTICULAR ACFT IN ACCORDANCE WITH ACFT MAINT MANUAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE ACFT ARRIVED WITH A PLT'S RPT OF MODERATE TO SEVERE NOSE GEAR VIBRATION ON TKOF AND LNDG. THE RPTR SAID THE NOSE GEAR WAS JACKED AND THE WHEELS SPUN; WHICH REVEALED THE NOSE GEAR TIRES WERE OVAL SHAPED AND WERE THE SOURCE OF THE SHIMMY. THE RPTR SAID BOTH NOSE GEAR TIRES WERE REPLACED PER THE MAINT MANUAL WITH SVCABLE TIRE AND WHEEL ASSEMBLIES AND WERE ROTATED BEFORE AND AFTER CORRECT TORQUE APPLIED TO THE AXLE NUTS. THE ACFT WAS DISPATCHED AND AFTER TKOF WAS UNABLE TO RETRACT THE NOSE LNDG GEAR AND A FLY-BY REVEALED THE NOSE GEAR WHEELS AT 90 DEGS. THE RPTR STATED WHEN THE ACFT TOUCHED DOWN THE WHEELS ALIGNED NORMALLY. THE RPTR SAID THE NOSE LNDG GEAR WAS CHKED AND IT WAS DISCOVERED THE R WHEEL BEARINGS HAD SEIZED. THE RPTR STATED THE FAA WAS INVESTIGATING THE BEARING FAILURE AND A LETTER WAS SENT TO THE RPTR. THE RPTR SAID THE ENTIRE NOSE LNDG GEAR WAS REPLACED AFTER THIS INCIDENT. SUPPLEMENTAL INFO FROM ACN 431536: WHEN WE BROUGHT THE GEAR LEVER SELECTOR TO THE 'UP' POS; AFTER A POSITIVE RATE OF CLB; THE NOSE GEAR DID NOT GO UP AND WE RECEIVED AN UNSAFE/NOT UP AND LOCKED INDICATION ON OUR EICAS. QRH HAD US CYCLE THE GEAR AND WE HAD 3 DOWN AND GREEN INDICATIONS. WE TALKED WITH MAINT AND DISPATCH AND WE ALL AGREED TO DO A FLY-BY TO MAKE SURE GEAR WAS OK; AS IF NOSE/TAXI LIGHT WERE ON; IT WAS REALLY DOWN AND LOCKED. WE EXECUTED A FLY-BY AT 500 FT AGL AND ON THE MISSED APCH WERE TOLD THAT THE NOSE GEAR WAS COCKED 75 DEGS TO R OF CTRLINE. ON GND; WE LOOKED AT R TIRE ASSEMBLY AND THE BEARINGS WERE DISINTEGRATED AND THE TIRE WAS HANGING ON BY A PIN AND A PIECE OF SAFETY WIRE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE R NOSE TIRE AND WHEEL ASSEMBLY FAILED DUE TO A WHEEL BEARING BEING INSTALLED BACKWARDS BY THE SHOP. THE RPTR SAID MAINT ADVISED THAT THE REASON THE NOSE GEAR STRUT CTRING CAMS DID NOT STRAIGHTEN THE WHEELS WAS THE LOWER STRUT WAS TURNED APPROX 75 DEGS TO THE R OF CTR AND TURNED BEYOND THE 40 DEG LIMIT OF THE CTRING CAMS. THE RPTR SAID HE HAS 500 HRS ON THE EMB145 AND HAS EXPERIENCED ONLY LIGHT NOSE GEAR SHIMMY.