~Causes of Wheel Bearing Failure ~

~Bearing life is limited by the following factors:~

• Contamination of the lubricant
• Lack of attention to bearing installation and maintenance
• Too little or too much lubricant
• The type of grease used.

~Contamination of the lubricant may be due to: ~

• Dirt from careless handling and storage of the bearing prior to installation
• Not thoroughly removing old grease from bearings and hubs
• Repacking bearings while still wet with cleaning solvent
• Using wet or contaminated air during the drying process
• Entry of water  or dirt from faulty or  incorrectly fitted seals.

~Lack of Attention to Old Bearings~

• Poor inspection of bearings after cleaning, resulting in the re-assembly of damaged bearings (etched, cracked, rusted, dented or in otherwise poor condition)
• Spinning dry bearings with a air-blow gun
• Adjustment too tight or too loose
• Not greasing immediately after cleaning  (once dry)
• Use of impact tools including a hammer and punch. Bearing cups or assemblies should be pressed into hubs and housings.

~Service Intervals~

• As the moving parts of a bearing come into contact with the grease, a small quantity of oil  will adhere to the bearing surface. Therefore, the life of a grease is restricted to the amount of oil which can reasonably be extracted for lubrication purposes. Oil that is picked up is gradually broken down by oxidation or lost by centrifugal force and must be replaced from the reserve held within the grease packing. Not only does regular cleaning and repacking replenish the lubricant supply, removal of old grease cleans the bearing surfaces of dirt, oil depleted grease, abrasives, moisture, ect.
• Greasing intervals depend upon the conditions under which the bearing operates and should be carried out at periods as recommended by the vehicle or bearing manufacturer.

~How To Prevent Wheel Bearing Failure ~

• Clean bearings properly. Use clean solvent and brushes and dry thoroughly with clean air.
• Never spin dry bearings; this causes scratching of the polished surface and may result in premature failure.
• Do not pack the bearing unless it is perfectly dry.
• Pack the bearing immediately following cleaning, drying and inspection.
• Do not use an excessive amount of grease - be sure it is worked into every bearing space, but do not fill the hub with grease.
• Keep bearings clean, work on a clean bench and do not handle bearings with dirty or moist hands.
• When re-assembling check the bearing for proper seating.
• Check adjustments carefully. Most vehicle manufacturers nominate a torsion wrench setting for bearing assemblies. Use a torque wrench and do not exceed the manufacturers recommendation.
• Keep grease containers completely covered when not in use to avoid contamination.  (Replace the lid immediately sufficient grease has been removed from the container).
• Do not mix different types of grease.  Never mix lithium based multi-purpose grease and soda base wheel bearing grease or an adverse chemical reaction will occur.
• Carefully avoid contact of the packed bearing with dirt, dust, water or dirty hands.
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