This investigation was opened based on 78 consumer complaints of severe suspension and steering wheel oscillations after the subject vehicles traveled over an uneven surface.ODI was concerned about these complaints because many of them alleged loss of control and the loss of control occurredat speeds above 50 miles per hour.at the time these complaints were received, ODI was also aware of the tsb 07-10-10 and early warning field reports that discussed the shimmy condition on the subject vehicles.since opening this investigation, ODI has confirmed, based on consumer complaints, warranty data, testing conducted by VRTC, and ODI inspection of complaint vehicles, that the owners of the subject vehicles are experiencing shimmy events on their vehicles.however, ODI has also confirmed that owners typically do not maintain their tires at the pressures recommended by Ford on the tire label.further, ODI has found that in order for shimmy to occur, tire pressures must be substantially below (at least 20%) those specified on the vehicle tire label.ODI considers these unsafe tire conditions to be the result of one of three typical situations.the tires are being improperly maintained, the owners are intentionally setting the tire pressures low to enhance ride quality, or aftermarket tires (not designed for use on the vehicle) are installed to change the appearance or function of the vehicle.the subject vehicles are intended and designed to be used as heavy duty vehicles and as such require that the tires be capable of handling the loads for which the vehicle is designed and marketed.in order for the tires to be capable of handling these loads, the proper tire pressure must be maintained.in light of the information gathered in this investigation and Ford's agreement to notify subject vehicle owners (now and every two years until the vehicles reach ten years from their production date) about the importance of maintaining proper tire pressures on their vehicles, further use of Agency resources does not appear to be warranted.the closing of this investigation does not constitute a finding by NHTSA that no safety-related defect exists.the Agency reserves the right to take further action if warranted by the circumstances.for additional information, see the attached closing report.
