Steering head and steering head bearings

The steering head is the short tube at the front of the frame through which the fork's steering stem passes. Its angle defines the bike's rake. Inside are the steering head bearings, usually tapered roller bearings (older bikes may have loose ball bearings), which let the fork turn while carrying braking and cornering loads.

Worn bearings cause a notchy feeling where the steering 'clicks' into the straight-ahead position, a clunk under braking, or play when you rock the fork with the front brake on. Both symptoms can lead to vague handling and wobbles.

Check with the front wheel off the ground: the bars should swing freely from lock to lock without notches, and there should be no play. Adjust preload to spec, and replace and grease bearings when worn, especially on bikes washed often with a pressure washer.