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All About Wheel Bearings

Without wheel bearings a vehicle would not get very far, it is these simple mechanical devices that allow the wheels to freely rotate without seizing due to friction. In a typical rear wheel drive automobile there are rear wheel bearings that are located at the actual wheel and axle bearings that are located towards the differential. There are several types of bearings used in the wheel and axle assembly of an automobile but they all serve the same purpose.

Types of bearings:

  • Ball type: This type of bearing is very common; it consists of a series of high precision steel balls held in place by a pressed steel cage. The balls run in between the inner ball race and the outer ball race, depending on the application one or the other of the races is held stationary while the other rotates. The assembly is sealed, in the majority of cases there are seals on both sides and the ball assembly is pre-lubricated with high temperature grease. Ball type rear wheel bearings can handle loads from either direction; sideways thrust and vertical radial.
  • Tapered roller bearings: At first glance it may appear that the rollers are cylindrical but they are not, all the rollers in this type of bearing are tapered in one direction. The tapered rollers nest into a conical shaped bearing race. These bearings are most frequently used in wheel bearing assemblies which in turn are mounted in a wheel hub. Tapered roller bearings can take heavy loads, both radial and thrust and can stand heavy shock loads which make them ideal for automotive applications.

Bearing lubricant:

Automotive bearings are pre-lubricated using either petroleum based or synthetic grease. Regardless of the type, the grease provides excellent lubrication for high friction surfaces at high temperature. The grease in held in the ball or roller races by seals.