Quarter Fender Failures

The Office of Defects Investigation (ODI) opened this Preliminary Evaluation (PE21-015) based on one Vehicle Owner Questionnaire (VOQ) and supporting fleet reports. The reports indicated that the subject quarter fenders were prone to cracking and/or separation.After a comprehensive review of the data related to the quarter fender failures on the subject vehicles, ODI did not identify the existence of a safety-related defect trend. Quarter fender failures resulted in a warranty claim rate less than one percent (<1%) of the total vehicle population. All separations, including those due to tread separations, road hazards, etc., accounted for less than point one percent (<0.1%) of the total vehicle population.ODI discovered that the minimum recommended gap between the top of the quarter fender and the bottom of the trailer was not known or being followed. The optional quarter fenders were supplied by Fontaine Spray Systems (FSS), who recommended a two inch (2) gap. ODI analyzed the claim data using a calculated gap. A calculated gap using the top of the quarter fender flap and assuming the trailer is level with the top of the fifth wheel hitch was necessary, as PACCAR doesn't know specifically what trailer a purchaser will couple to the tractor. It is safe to assume no trailers on the market extend below the upper fifth wheel plate, but many do provide additional clearance over the wheels where the quarter fenders are located. ODI determined that 94 percent of warranty claims and 84 percent of separations violated FSS' recommendation.ODI confirmed that the VOQ vehicle and the fleet report vehicles also violated FSS' recommended gap. In one fleet the gap was negative point three inches (-0.3).PACCAR has updated its vehicle specification process and issued a customer advisory notice to existing owners. In light of the low rate of reported failures and separations, 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.