Which of the following is NOT listed as a common bearing failure mode?

• A. Wear
• B. Spalling
• C. Lubrication starvation
• D. Contamination

Answer: (D)

Contamination is not listed as a common bearing failure mode because it’s best thought of as a contributing factor that speeds up damage, rather than a distinct mode of failure by itself. Bearings typically fail through clear damage mechanisms such as wear, where material is gradually removed by sliding contact; spalling, which is fatigue cracking that causes flakes to break away from raceways or elements; and lubrication problems like starvation, where insufficient or degraded lubricant leads to excessive metal-to-metal contact and overheating. Contaminants—dirt, dust, water—tend to accelerate these processes by increasing abrasive wear, promoting corrosion, or clogging lubrication paths, but they don’t represent a separate failure mechanism on their own.