How often do ball bearings need to be replaced?

Determining Ball Bearing Replacement Intervals

1. Countdown begins when unusual noises appear.
Initial rustling noise: Minor scratches on the raceway, metal powder mixed with grease (cleaning and regreasing can be postponed, but the lifespan is halved).
Continuous humming noise: Raceway fatigue peeling, bearing clearance exceeded (replace within 2 weeks).
Sharp scraping noise: A precursor to rolling element breakage (stop the vehicle immediately!).

2. Frame looseness is a safety red line.
Wheel bearing: A "clicking" feel when pressing the tire with your finger (exceeding 0.5mm of axial play).
Steering bearing: A "nodding" feel when squeezing the front brake handlebars (preload completely lost).
Testing tool: Axial displacement measured with a dial indicator > manufacturer's manual limit.

3. Seal failure triggers mandatory replacement.
Rubber oil seal: Cracks/hardening/deformation (loss of dustproofing capability).
Grease leakage: Black mud or rust seeping from the bearing housing (internal contamination).
Grease hole blockage: New grease cannot be pressed in after three injections (internal grease has dried out).

4. Overheating indicates an emergency.
Short-term temperature rise: The bearing seat becomes hot (>70°C) when touched by a finger for 3 seconds.
Burning odor: Grease carbonization (possible locking within 48 hours).
Infrared inspection: Temperature difference >15°C across the coaxial axis (one-side bearing damage).

5. Special operating conditions accelerate scrapping.
Operating conditions: Early replacement cycle.
Off-road muddy and wet terrain: Normal life x 0.3 (must be inspected after rain).
Modified and weighted wheels: Normal life x 0.5 (increased impact).
Long-term storage: Rusting: Disassemble and inspect to confirm raceway rust depth.
Deformation due to impact: Replacement is mandatory regardless of any unusual noise.

6. Preventive replacement criteria (when no faults occur).
Commuter motorcycles: Every 30,000 km/two years (whichever occurs first).
Competitive motorcycles: Every 15 track hours or at the end of the season.
Old bearings: Replacement recommended even if in good condition after more than six years.