Wheel Spindle
The metal shaft extending from the steering knuckle upon which the wheel hub and bearings are mounted.
A wheel spindle is a high-strength metal shaft or pin that projects outward from the steering knuckle on vehicles, particularly on non-drive wheels (like the front wheels of rear-wheel-drive vehicles). It serves as the mechanical axis for the inner and outer wheel bearings, the wheel hub assembly, and the brake rotor or drum.
The spindle must be designed to withstand severe shear forces, carrying the full weight of the vehicle and absorbing road shocks and cornering loads. The end of the spindle is typically threaded to accept a spindle nut, which is torqued to set the wheel bearing preload and locked in place with a retainer or cotter pin.
Spindles can become bent or cracked due to collision impacts, curb strikes, or extreme wheel bearing failure (which can generate enough heat to weld the bearing to the spindle shaft). A damaged spindle will cause wheel misalignment, bearing noise, and potential wheel detachment, requiring replacement of the steering knuckle or spindle assembly.