NHTSA Preliminary Evaluation PE97033

IN ADDITION TO THE A FAILURE REPORT TABULATIONS GIVEN ABOVE, THE MANUFACTURER REPORTED THAT AN ADDITIONAL 33 OWNER AND FIELD REPORTS HAVE BEEN FILED WHICH REFER TO PROBLEMS (LUG NOT TORQUE LOSS, LUG BOLT FRACTURE) THAT DID NOT INVOLVE ACTUAL WHEEL SEPARATION, BUT WHICH MAY BE POTENTIALLY RELEVANT EVENTS.THE MANUFACTURER ALSO REPORTED THAT A TOTAL OF 815 WARRANTY CLAIMS HAVE BEEN FILED FOR REPAIRS POTENTIALLY RELATED TO THE MATTER BY PURCHASING THE VEHICLES BACK FROM OWNERS AS A GOODWILL MEASURE.THE WHEEL SEPARATIONS CITED IN THIS PE INCLUDE MANY WHICH OCCURRED WITH THE VEHICLE BEING DRIVEN; IN THESE CASES SOME PROPERTY DAMAGE TO THE VEHICLE ITSELF ALMOST ALWAYS RESULTED FROM COLLAPSE OF THE SUSPENSION .THE CRASH INCIDENTS CITED IN THE TABULATIONS ABOVE ARE LIMITED TO THOSE INCIDENTS IN WHICH DAMAGE WAS ALSO SUSTAINED BY A SECOND VEHICLE OR A FIXED OBJECT.THERE ARE INDICATIONS THAT PROBLEMS OF LUG NOT TORQUE RETENTION HAD BEEN EXPERIENCED DURING VEHICLE FINAL ASSEMBLY, AND FAILURE ANALYSES INDICATE THAT LUG NUT TORQUE LOSS COULD RESULT IN FATIGUE FAILURE OF THE LUG BOLTS. THERE ARE ALSO INDICATIONS THAT UNDER CERTAIN CONDITIONS, THE LUG NUTS MAY BE UNUSUALLY SUSCEPTIBLE TO OVER-TORQUING, RESULTING IN PLASTIC DEFORMATION OF THE LUG BOLTS WHICH IN TURN, COULD LEAD TO FATIGUE FAILURE.DUE TO THE OPEN ISSUES AND QUESTION RAISED BY THE PE, THIS MATTER HAS BEEN UPGRADED TO AN ENGINEERING ANALYSIS.