A Definitive Guide to Your Car’s Wheel Bearings and Hub Assembly

Wheel bearings play an important role in the way your vehicle functions as these are an integral part of your vehicle’s wheel. Think of it as an assembly that connects your car’s wheels to the cv joint.

Your wheel bearings serve three main purposes:

  • Support the vehicle’s weight
  • Absorb axial and radial forces
  • Enable your wheels to rotate freely with minimal friction

When your wheel bearings fail, these functions can quickly become impaired. A compromised wheel bearing can limit the driveability of your vehicle and can seriously impact your safety by causing your wheel to fall off.

Defining wheel bearings

Wheel bearings are categorized as generation 1, 2, or 3. The steel components (e.g., rolling element, flange, etc.) of a wheel bearing are manufactured and engineered with certain specifications. This is necessary as wheel bearings must endure considerable abuse such as poor road surfaces, severe weather conditions, or other challenging driving conditions. More additional information is shown below:

  • Generation 1 wheel bearing — This is simple and compact which consists usually of two pairs of rolling elements without pre-load requirements.
  • Generation 2 wheel bearing — Improved generation one with mounting holes, flange, and clamps for a more accurate installation.
  • Generation 3 wheel bearing — The latest version of the wheel bearing series with the following specifications:
    • Configured for preload
    • Built-in flanges makes installation easy (e.g. to the chassis, disc brake, etc.)
    • Sensors for wheel speed are included for cars with ABS capabilities

The role of bearing lubricant

Because wheel bearings are supposed to be maintenance-free parts, they must be adequately sealed with lubricant, though some of the latest versions such as the generation 3 ones are pre-lubricated.

Proper lubrication diffuses heat produced by the rolling elements, prevents the entry of foreign contaminants, and maintains the operational efficiency and integrity of the bearings. Depending on the application, the load, and the operating environmental conditions, different grease types are available from top bearing manufacturers.

Wheel bearing warning signs and symptoms

While periodic maintenance may be required, a wheel bearing may require repair before its expected service life. Regardless of the type, the warning signs are more likely the same.

Any unusual operating behavior will be visible through these identifiable symptoms:

  • Grinding or grating during acceleration
  • Snapping or clicking while steering
  • Rumbling, humming, or growling while driving straight
  • Wheel vibration or wobble
  • Excessive runout
  • Abnormal or uneven tire wear
  • Steering wheel pull
  • Steering wheel vibration grinding or grating near or around

While these are common symptoms for a faulty wheel bearing, they are also associated with other drivetrain and suspension system components. Uneven tire wear, for example, can mean a misalignment, improper inflation, or damaged suspension parts.

Perform the correct diagnosis to determine which component is at fault. For instance, if the complaint is a wheel bearing noise, perform a test drive. Doing your due diligence is important to save on maintenance and labor costs.

Inspecting wheel bearing damage

Carefully examine the damage patterns present on the wheel bearing. This will allow pinpointing the root cause of the problem.

While the list below is not an exhaustive guide, it highlights the most common damage patterns to look out for on a faulty wheel bearing.

Corrosion

Wheel bearings are typically sealed units. Any moisture that enters the bearing can inevitably corrode it. A corroded wheel bearing has diminished grease performance, resulting in extensive wear and overheating.

This can be a result of poor service installation or other driving circumstances. Follow the manufacturer’s guidelines to avoid future corrosive damage.

Cage damage

Often associated with roller bearings, cage deformation can appear as a bent cage or rollers binding and skewing. This is due to improper installation. Any cage deformation results in the bearing being unusable. Replace bearing and follow proper installation procedures.

Brinelling

There are two types of brinelling found in bearings: true brinelling and false brinelling. Both appear as surface indentations in the bearing raceway. True brinelling appears as regularly spaced indentations, while false brinelling is displayed as depressions and wear marks.

True brinelling can be caused by excessive loads or impact. False brinelling occurs through vibration. Both use different preventive methods.

True brinelling can be prevented by using correct installation tools and careful handling procedures. False brinelling should be secured during transport to eliminate external vibration.

Spalling

Spalling can occur due to incorrect mounting or removal, excessive pre-load and radial load, deformed bearing components, and poor lubrication of rolling elements. Scoring on the raceway surface and rolling contact surface is indicative of spalling.

Spalling can be addressed by selecting adequate lubrication, improving mounting and removal procedures, using recommended mounting tools, and correct pre-load.

Overheating

The discoloration is the most visible sign of overheating mainly due to inadequate lubrication. Grease contamination and inadequate heat paths can also be contributing factors. Effective cures for overheating include using the correct grease type for the application and by providing heat paths.

Cracks

Cracks that appear on rolling elements or the raceway surface can be indicative of excessive load, shock load, excessive interference, improper fit, and poor bearing seats, among other symptoms. When left in continued use, cracks can deepen and lead to fractures.

Advisable solutions include replacement of bearing and correction of load conditions.

Misalignment

Misalignment can occur during service installation or through the entry of foreign objects. A non-parallel path of rolling elements can indicate misalignment. If the bearing is misaligned beyond its maximum allowance, the bearing will have a premature service life.

Check the manufacturer’s specified limits. Re-adjust the bearing alignment as required. Confirm that the races are properly sealed.

Conclusion

While bearing manufacturers have created design changes to improve bearing performance, all drivers and licensed professional mechanics or your area’s trusted bearing distributor should be aware of key bearing damage causes and their symptoms.

If any of the symptoms or damage patterns above present themselves, wheel bearing maintenance should be performed. Continued use of a faulty wheel bearing can result in severe mechanical damage and road accidents.

This can help save considerable time and money while also prolonging the service life of the bearing.

Author bio

Hassanein Alwan is the Managing Director of Mineral Circles Bearings with more than 10 years’ experience in the bearing industry’s technical support division, sales, and marketing, plus strategic business development consultancy.