On a typical passenger vehicle weighing around 3,400 pounds, each pair of front-wheel bearings, as well as the rear-wheel or axle bearings, support around 850 pounds depending on the weight distribution and driveline configuration. If it’s a 6,000-pound SUV, each bearing might carry about 1,500 pounds. This load is concentrated on the relatively small bearing surfaces. These loads do not even take into account the dynamic loads produced by cornering.
Bearings are precision products that require complex manufacturing processes. Inferior bearings that use low-quality steel and have poor heat-treating can prematurely wear and spall. The poor-quality steel may have inclusions of hard or soft metal that can cause a premature failure. In summary, an inexpensive bearing may look the same as a high-quality bearing, but it is what you can’t see that makes a difference between a comeback and a satisfied customer.
In addition, some cheaper hub units are using smaller bearing sizes than the OEM intended. This can also lead to premature failure. Unfortunately, the only way to tell is to destroy the new bearing.
A high-quality bearing is a key to performing a comeback-free job. High-quality hub units or bearings typically use higher-quality materials and heat-treating processes that make for harder surfaces. The harder surfaces will not “Brinell” under hard impacts.
When replacing a hub unit, the replacement unit might feel stiff and difficult to turn. Do not return the bearing. Some hub units and sealed bearing are filled with a special grease that prevents damage while the bearing is being shipped. The grease is designed to have a high viscosity during shipping, so the balls or rollers do not destroy the surfaces of races. After the bearing is installed, certain elements in the grease break down, and the bearing turns normally.
While it may appear to be easier to use an impact wrench during service, it is not recommended. OEM and bearing manufacturers always recommend using a torque wrench for installation. During removal, an impact wrench can damage the axle nut threads and shock the CV joints. It can also create a false sense of security when adjusting a nut or bolt, which may be under- or over-torqued. This can leave a hub assembly susceptible to failure. Also, in almost all cases, use a new axle nut. Some axle nuts are designed to be used only once and cannot be adjusted.
This video is sponsored by bproauto.
