Which of the following is a valid sign of bearing wear?

• A. Visible corrosion on the bearing housing.
• B. Excessive noise, heat, vibration, rough rotation, and visible wear or scoring on races.
• C. The bearing grows in size during operation.
• D. A bearing that has cooled is a sign of wear.

Answer: (B)

Excessive noise, heat, vibration, rough rotation, and visible wear or scoring on the race surfaces are classic signs that a bearing is worn. When the rolling elements and races wear, contact becomes harsher and less smooth, which shows up as louder operation and more vibration. The extra friction from worn surfaces causes heating, especially if lubrication isn’t optimal. Rough rotation is felt as stiffness or grittiness as the internal clearances change and the surfaces are damaged. Visible wear or scoring on the races confirms that the bearing surfaces themselves have deteriorated and are no longer providing proper, smooth rolling. Other signs like housing corrosion, a bearing growing in size during operation, or cooling instead of heating do not directly indicate bearing wear and point to different issues such as environmental exposure, abnormal thermal expansion, or lubrication/thermal management problems.