The wheel hub assembly is the central rotating component at each wheel position that connects the wheel and tyre to the suspension system, transmitting drive torque on driven axles while supporting the vehicle weight through the wheel bearing. On modern vehicles, the hub is typically a flanged shaft pressed into or bolted to the wheel bearing, with a splined central bore that accepts the CV axle shaft (on driven wheels) and five or more wheel bolt holes in the flange. On non-driven axles, the hub is a solid stub shaft rotating in the bearing. The hub also provides the mounting flange for the brake disc, which bolts or presses onto the hub face. Hub geometry is critical — the bolt circle diameter, pilot diameter, and offset dimension determine which wheels will fit without clearance problems. The hub's dimensional tolerances, particularly the runout (wobble) of the wheel flange face, directly affect brake disc runout — a hub with excessive face runout will cause disc thickness variation and brake pedal pulsation regardless of the quality of the disc installed. Hub assemblies are replaced when the integrated bearing fails, when the flange is damaged (cracked, stripped bolt holes, or excessive corrosion), or when a brake disc runout problem is traced to hub face runout rather than the disc itself.
On driven axles, the hub transfers engine torque from the CV axle shaft to the wheel. The splined central bore engages the outer CV joint's splined stub shaft, and the hub nut torqued to specification clamps the hub onto the splines. Torque transfer is through these splines, which must be clean and undamaged for efficient power transmission and to prevent fretting wear. On all axles, the hub provides the mounting surface for the brake disc — the disc's rotational precision depends entirely on the hub's face runout. A perfectly flat disc on a hub with 0.05mm of face runout will show the same 0.05mm runout on the disc face, and will cause pedal pulsation as if the disc itself were warped. Hub runout is measured with a dial gauge on the wheel flange before disc installation during brake work — any runout greater than 0.05mm at the flange face should be investigated. The hub's wheel bolt holes transmit all braking and acceleration forces from the wheel to the suspension through the bolts — stripped or damaged bolt holes require hub replacement before any other consideration.
Hub face runout causing brake pulsation: Often misdiagnosed as warped brake discs. After disc replacement fails to resolve pedal pulsation, measuring the hub face runout with a dial indicator identifies whether the source is the hub rather than the disc. Hub runout exceeding 0.05mm typically requires hub replacement to resolve persistent brake pulsation.
Corrosion bonding the disc to the hub: Galvanic corrosion between the steel disc and cast iron hub face creates a thick rust layer that prevents the disc from seating flat. This causes immediate brake disc runout after installation of new discs on a corroded hub. Wire brush the hub face thoroughly before any disc installation — the face must be clean, flat, and free of any raised corrosion or debris.
Stripped or damaged wheel bolt holes: Over-torquing wheel bolts or using an impact wrench without a torque stick strips the hub's threaded inserts or wheel stud holes. Stripped bolt holes are dangerous — the wheel cannot be securely fastened and must not be driven on. Hub replacement is required.
Level 1 — Wheel Attachment Inspection: Check that all wheel bolts are present and properly torqued at every tyre rotation. Finger-tighten bolts before using the torque wrench — cross-threading a bolt from incorrect start angle is a common cause of stripped threads. Inspect the wheel seating surface and hub face for corrosion buildup whenever wheels are removed.
Level 2 — Hub Face Cleaning at Disc Service: Clean the hub face with a wire brush, removing all rust scale, paint, and debris, every time brake discs are removed or replaced. A corroded hub face is the primary cause of new disc runout and subsequent brake pulsation. The hub face must be clean bare metal, flat, and free of any raised material before the new disc is seated. Check hub face runout with a dial indicator if previous brake disc replacements have not resolved pulsation.
Level 3 — Professional Hub Replacement: Hub assembly replacement on a driven axle requires removing the CV axle and the hub nut, pressing or unbolting the bearing unit, and pressing the new hub into the bearing. On non-driven axles, the hub and bearing may be an integrated assembly pressed from the knuckle. After hub replacement, torque the hub nut to the exact specification — under-torquing allows the hub to move on the CV shaft splines; over-torquing damages the bearing preload.
Describe the sound or symptom to OOG-E and get a read on what's going on.