This Service Bulletin addresses the issue of brake shimmy in Meritor® SteeLite X30™ brake drums exhibiting excessive runout. It provides guidance for Freightliner truck models including: FLA COE, FLB COE, FLD Conventional, Business Class, FLC 112 Conventional, Century Class Conventional, Argosy COE, Cargo, Columbia, Coronado, Business Class M2, Cascadia, and 108SD/114SD. The bulletin outlines the problem, potential causes, and recommended solutions to resolve the brake shimmy issue.

## Addressing Brake Shimm in Freightliner Trucks: A Focus on SteeLite X30 Brake Drums Freightliner trucks, spanning diverse models like the FLA COE, FLB COE, FLD Conventional, and more, are known for their reliability and performance in the demanding world of commercial transportation. These trucks, built for hauling a wide range of cargo, rely heavily on their braking systems to ensure safe and efficient operation. One critical component of these braking systems is the brake drum, responsible for converting kinetic energy into heat through friction. The Meritor SteeLite X30 brake drum, a popular choice for many Freightliner models, offers durability and weight savings. However, excessive runout in these drums can lead to brake shimm, a condition that manifests as a noticeable vibration during braking. This vibration not only compromises driver comfort but can also negatively impact braking efficiency and potentially lead to premature wear on other components. Brake shimm in Freightliner trucks equipped with Meritor SteeLite X30 brake drums can stem from various factors like improper installation, wear and tear, or manufacturing defects. The phenomenon arises when the brake drum's surface deviates from its intended circular shape, leading to uneven contact between the brake shoes and the drum. This uneven contact causes oscillations in brake pressure, resulting in the characteristic shimm felt by the driver. Addressing this issue is critical for maintaining consistent braking performance, extending the lifespan of the braking system, and ensuring overall driver safety. Identifying the cause of the runout, whether stemming from a worn drum, misaligned components, or other issues, is crucial for implementing effective corrective measures. Mechanics often utilize specialized tools and techniques to measure the runout and determine the best course of action, ranging from replacing the drum to adjusting the brake components.