When to replace a ball bearing?

Here's when to replace a ball bearing:

1. Your Ears Catch Trouble

Grinding/Growling: A low, metallic sound (like sandpaper grinding on an iron pipe) that increases with speed.
Clicking/Clunking: A "clicking" sound at specific angles (the ball bearing bounces in the spalling pits).
High-frequency squealing: The harsh sound of dry grinding caused by lubrication failure.

2. Hands Feel the Damage

Axial play: A "clicking" sound occurs when you press your finger against the component and shake it (steering column bearings >1mm are considered high-risk).
Steering Jam: A noticeable resistance point or a sticky feeling during rotation (pitted spots in the raceway are causing the ball bearing to become stuck).
Abnormal Vibration: A high-frequency, fine vibration felt when you grip the handlebars or pedals (the raceway is out of round).

3. Eyes See the Evidence

Grease Leakage: Black, muddy oil or rusty water seeping from the bearing housing (seal failure)
Cracked Oil Seal: Hardened and cracked rubber dust seal (>3 cracks must be replaced)
Discoloration from Overheating: Blue/yellow discoloration of the bearing seat (heat damage exceeding 250°C)

4. After Critical Events

After a Crash or Impact: Regardless of symptoms, the bearing must be replaced (internal microcracks are not visible)
After Deep Water Immersion: The wheel bearing is submerged in water deeper than the wheel axle height (mud and sand intrusion is irreversible)
After Overloading: The load exceeds the vehicle's weight limit by >30% and produces abnormal noises

5. Performance Red Flags

Steering Feel Dull: The handlebars feel sticky when cornering (steering bearing preload failure)
Abnormal Brake Vibration: High-frequency vibration of the handlebars when braking lightly (transmitted from the wheel bearing frame to the disc rotor)
Abnormal Wheel Hub Spin: The wheel stops within half a turn when gently pushed (sudden increase in rolling resistance)

6. Ultimate Red Flag

Burning smell + smoke: Grease carbonization, bearings on the verge of sintering. Rotational lock: Any degree of binding (can instantly lock up in a corner!). Loose components: The wheel is visibly tilting (the inner race of the bearing is slipping on the journal).