The Most Common Bearing Failures and How to Prevent Them

by Kevin Sweeney
25 May, 2023
7 min read

Bearings are important for optimal functioning of mechanical systems. Bearings support the weight of rotating shafts and contribute to reduced friction. Poor bearing performance can lead to expensive repairs, and in some cases, catastrophic breakdowns. This article aims to understand and explain the distinct kinds of bearing failures, their root causes, warning signs, and prevention measures.

Types of Bearing Failures

The most common types of bearing failures are Overheating, Contamination, Inadequate Lubrication (including Excessive and Incorrect Lubrication), Misalignment, Corrosion, Brinelling, Electrical Pitting, Improper Mounting, and Bad Fits.


Excessive operating temperature is a leading cause of bearing failure. When a bearing’s temperature exceeds its recommended limit, failure can occur. Excessive temperatures are due to inadequate lubrication, excessive loads, or a combination of both.

Discoloration caused by excessive heat from poor lubrication

Elevated temperatures cause the lubricant to break down, reducing its effectiveness in preventing metal-to-metal contact. Overheating can lead to premature wear, fatigue failure, and bearing seizures.

  • Inner ring of an angular contact ball bearing
  • Symptom: Bluish or purplish Discoloration on raceway surface
  • Contamination

Lubrication contamination is another common cause of bearing failure. It can occur due to foreign particles, such as dirt, dust, moisture, or anything entering the bearing. Contaminants cause the lubricant to become abrasive, a source for corrosion and surface damage like pitting, and leading to premature wear and failure.

Inadequate Lubrication

Inner ring of a spherical roller bearing

Inadequate or lack of lubrication is a common cause of bearing failure. Proper lubrication is a crucial factor in reducing friction and preventing metal-to-metal contact. Insufficient lubrication leads to increased friction, overheating, and premature wear.


Misalignment occurs when the bearing is not correctly aligned with the shaft or housing. It can cause uneven loading and increased stress on the bearing, leading to premature wear and eventual failure.


Corrosion can occur due to exposure to harsh environments, salt water, blood, and numerous other things including chemicals. Corrosion causes pitting, cracking, and surface damage, leading to premature wear and eventual failure.


Inner ring of a deep groove single row ball bearing

Brinelling is a permanent indentation in the raceways of the bearings. Brinelling is the permanent plastic deformation of the bearing surface and occurs when the rolling elements (ball or rollers) and the raceway’s material yield strength has been exceeded.

The indentations in the raceways can quickly lead to chattering and excess vibration, which in turn can accelerate other forms of wear, such as spalling and ultimately lead to failure of the bearing.

Spalling is the pitting or flaking away of bearing finish that occurs in the races and on the rolling elements.

Electrical Pitting

Electrical Pitting can occur due to stray electrical currents passing through the bearing. It can cause damage to the bearing surface, leading to premature wear and eventual failure.

Improper Mounting and Poor Fits

Improper mounting can cause alignment issues, uneven loading, and stress on the bearing, leading to premature wear and eventual failure. Poor Fits will cause creep in the bearing.

Symptoms of Bearing Failure

It is essential to identify the symptoms of bearing failures early to prevent catastrophic failure. Some of the symptoms of bearing failure include:

  • Excessive noise or vibration
  • Increased bearing temperature
  • Reduced performance or efficiency
  • Visible signs of wear or damage on the bearing surface
  • Lubricant contamination or discoloration
  • Unusual smells or odors coming from the equipment

How to Identify Each Type of Bearing Failure

Identifying the type of bearing failure can help determine the problem’s root cause and implement effective corrective actions. The following are some methods for identifying each type of bearing failure:

  • Overheating: Measuring the bearing temperature with a temperature probe can help in identifying overheating. A temperature above the recommended limit indicates potential overheating issues.
  • Contamination: Inspecting the bearing surface for visible signs of wear or damage can help in identifying contamination. Discolored or contaminated lubricant is also a sign of contamination.
  • Inadequate Lubrication: Inspecting the lubricant for signs of wear or discoloration can help identify inadequate lubrication.
  • Misalignment: Checking the alignment of the shaft and bearing using a laser alignment tool can help in identifying misalignment issues.
  • Corrosion: Inspecting the bearing surface for signs of corrosion, such as pitting or cracking, can help in identifying corrosion issues.
  • Brinelling: Inspecting the bearing surface for visible signs of indentation can help in identifying brinelling.
  • Electrical Pitting: Inspecting the bearing surface for visible signs of damage or pitting can help identify electrical pitting.
  • Improper Mounting: Checking the mounting of the bearing using proper installation procedures can help identify improper mounting.
  • Lubricant Breakdown: Inspecting the lubricant for signs of contamination or discoloration can help in identifying lubricant breakdown.

The Importance of Regular Inspections and Maintenance

Regular inspections and maintenance are essential for preventing bearing failures. Inspecting the equipment and bearings for signs of wear, damage, or contamination can help identify potential issues early. Proper lubrication and alignment are also critical for preventing bearing failures. Regular maintenance, such as bearing cleaning and lubrication, can also extend the life of the bearings.

Preventing Bearing Failures

Preventing bearing failures involves implementing proper maintenance and inspection practices. The following are some methods for preventing bearing failures:

  • Proper lubrication: Using the correct type and amount of lubricant can help in preventing bearing failures due to inadequate lubrication.
  • Regular maintenance: Performing regular maintenance tasks, such as bearing cleaning and lubrication, can help in preventing bearing failures.
  • Proper alignment: Ensuring proper shaft and bearing alignment can help in preventing misalignment issues.
  • Contamination prevention: Implementing contamination prevention measures, such as using protective covers and seals, can help in preventing contamination issues.
  • Load monitoring: Monitoring the load on the bearing can help in preventing overloading issues.

Bearing Repair and Replacement

If a bearing failure occurs, it is essential to repair or replace the bearing promptly to prevent further damage. Bearing repair involves inspecting the bearing surface for any damage, cleaning the bearing, and replacing any damaged components. If the damage is extensive, replacing the bearing may be necessary.


Bearing failures can lead to costly repairs, downtime, and even catastrophic failures. Understanding the types, causes, and symptoms of bearing failures is essential for preventing them. Proper maintenance and inspection practices, such as proper lubrication, regular maintenance, and load monitoring, can help prevent bearing failures. In the event of bearing failure, prompt repair or replacement is essential to avoid further damage. By implementing proper maintenance and inspection practices, bearing failures can be prevented and equipment life can be extended.

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Written by

Kevin Sweeney

Founder and CEO at Pacific International Bearing Sales Inc (PIB)
Education: BS Business and Economics California State University Hayward Ca
CBS (Certified Bearing Specialist)

My role with Pacific International Bearings (PIB) is currently CEO. Since 1976, I have been deeply involved in the bearing industry, working in manufacturing sales at NTN Bearing and subsequently in Bearing Distribution. Before establishing PIB in 1990, I gathered valuable experience in bearing manufacturing and distribution. The last 45 + years in the bearing industry have been both rewarding and challenging, assisting customers across a large number of diverse bearing applications.
Outside of the bearing industry, my interests are family, woodworking, motorcycling, cars, gardening, and golf.
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