NHTSA Preliminary Evaluation PE11007

ODI opened this preliminary evaluation based on a fleet report that it had experienced multiple wheel-end fires.The fleet believed this was due to the power spring fracturing and subsequently puncturing the diaphragm resulting in an air loss causing the brakes to drag.A vehicle driver suffered smoke inhalation during one of the fires suspected to have been caused by the alleged defect.Another injury was sustained by a mechanic when he attempted to remove the brake chamber with a broken power spring.The brake chamber sprung from its mounting bracket and struck the mechanic in the face, causing multiple lacerations.Brake chambers have a limited life span and are subject to wear out.However, the failures identified by the fleet are much earlier than expected and may not exhibit discernible failure symptoms.ODI initiated testing at the Vehicle Research and Test Center (VRTC) to determine the cause of the spring failure and to better understand any warning signs that may be present.VRTC's testing is ongoing as is Haldex's inspection of failed chambers returned from the fleet.This PE has been upgraded to an Engineering Analysis (EA11-011) to further evaluate the cause of the fires and assess the scope, frequency, and safety consequences of the alleged defect.