Which of the following is the most common cause of bearing failure related to lubrication?

The most common cause of bearing failure related to lubrication is insufficient lubrication or contamination. Adequate lubrication is critical for reducing friction and wear between the moving surfaces of bearings. When there is insufficient lubricant, the bearing components can come into direct contact, leading to increased wear, overheating, and ultimately failure.

Contamination can also significantly impact bearing performance. Contaminants, such as dirt, dust, or moisture, can be introduced into the lubricant, leading to abrasive wear and chemical breakdown of the lubricant. This can further compromise the lubrication properties, leading to insufficient protection of the bearing surfaces.

In contrast, while excessive lubrication can lead to issues such as aeration or foaming of the oil, which can reduce lubrication efficiency, it is less commonly the primary cause of bearing failure compared to insufficient lubrication. Improper installation can certainly lead to problems and failure, but it is not exclusively a lubrication issue. Overheating of bearing components may result from inadequate lubrication, but it is not a direct cause of lubrication failure itself.