Strut (see also Knee Assy)

How Struts and Knee Assemblies Function

A strut is a key structural component of the suspension system, combining the functions of a shock absorber and a support for the vehicle’s chassis and steering knuckle. The knee assembly incorporates the strut, spindle, and mounting components, ensuring correct suspension geometry and load transmission.

Signs of Worn or Failing Struts

Symptoms include excessive bounce, nose-diving during braking, uneven tire wear, and abnormal noises. Unchecked, these issues can lead to compromised safety, reduced comfort, and premature failure of related components.

Selecting and Installing Replacement Struts

Always choose struts and knee assemblies that match OEM specifications for your vehicle. Proper installation requires specialized tools and alignment procedures to ensure optimal ride quality and long-term durability.

Struts and knee assemblies have evolved as critical elements in modern automotive suspension systems, merging damping control and structural support into a single, highly engineered component. The MacPherson strut, for example, revolutionized vehicle design by integrating the shock absorber and coil spring into a compact unit, reducing complexity and weight compared to traditional double-wishbone setups. Knee assemblies, which include the strut housing, spindle, spring perch, and mounting brackets, play an equally vital role by maintaining correct wheel alignment and load paths between the chassis and road surface.

Historically, struts were introduced to simplify front suspension layouts while still providing precise steering and stable ride characteristics. The knee assembly concept further enhanced this by ensuring that all critical mounting and pivot points were robustly engineered and properly located. The assembly must withstand dynamic forces from acceleration, braking, and cornering while also absorbing vertical impacts from uneven roads. As vehicles have become heavier and more powerful, OEMs have engineered struts and knee assemblies with advanced materials—such as high-strength steel and aluminum alloys—to provide the necessary rigidity and resistance to fatigue.

Aging or damaged struts can cause a cascade of handling problems: they may allow excess suspension movement, leading to poor tire contact and unpredictable steering response. Over time, seals may leak, internal valving may wear, and bushings can degrade, all of which reduce the assembly’s effectiveness. This can result in longer stopping distances, increased body sway, and accelerated tire and suspension wear. Diagnosing strut or knee assembly failure often involves visual checks for oil leaks, bent housings, or excessive play, as well as road tests for abnormal body movement or noise.

Replacement should always prioritize OEM-type fitment to maintain geometry and performance, and installation often requires spring compressors, torque wrenches, and post-installation alignment. Neglecting to replace struts at the first signs of failure can compromise not only ride quality but also the safety and longevity of the entire suspension system. Advances in materials and manufacturing have improved both the durability and weight efficiency of modern assemblies, offering drivers longer service life and better ride performance. As a cornerstone of vehicle suspension technology, struts and knee assemblies demand attention to detail in both selection and installation to ensure optimal safety and handling.