1、 Understand the load capacity of the bearing.

On a typical passenger car weighing approximately 3400 pounds, each pair of front wheel bearings and rear wheel or axle bearings supports approximately 850 pounds, depending on weight distribution and powertrain configuration. If it is a 6000 pound SUV, each bearing may carry approximately 1500 pounds. This load is concentrated on the relatively small bearing surface. These loads do not even consider the dynamic loads generated by turning.

The load applied to the bearing is called thrust load and radial load. They are the forces that the bearings must withstand when the vehicle turns or brakes. Another force that cannot be measured is the impact of potholes and curbs.  

2、 Excessive grease is a bad thing

Overfilling bearings with excessive grease can cause excessive stirring of the grease during operation and at high temperatures, resulting in overheating and excessive grease removal (leakage). Overheating occurs because the generated heat cannot be dissipated correctly and continues to accumulate until damage occurs. When the bearing overheats and grease is squeezed out, the sealing lip may be damaged and blown out in the opposite direction.

3、 Firstly, diagnose the cause of bearing failure.

When bearings are worn, it is usually due to insufficient lubrication, incorrect installation, or improper adjustment. To make the repair successful, you must first determine the cause of previous bearing failures. For sealed hub units, it is not possible to inspect the internal bearings and race.

Firstly, understand the type of road they are driving. Also ask them what types of loads they usually carry in the vehicle. If the customer overloads the vehicle, bearing damage may be inevitable. The most common failure mode of bearings is when the bearings on the passenger side of the vehicle first fail. The passenger side bearing is exposed in the area with the most accumulated water on the roadside. If the bearing on the driver's side of the vehicle malfunctions first, please carefully check the bearing on the passenger's side, as their failure may follow closely.

4、 Oxidized oil is as bad as no oil.

Burning or oxidizing lubricants may leave a dark coating on the bearing surface. If the bearing overheats, the hot lubricant will decompose and cause scratches or even corrosion on the bearing surface. Water and other corrosive elements can also cause this situation, leading to peeling of the road surface. Please remember that for tapered roller bearings, excessive preload can simulate the same damage. If the bearing becomes very hot, the cage and seals may deform and cause the bearing to lock.

5、 Grease wear.

Lubricating grease is a precise combination of oil, thickener, and additives. Oil retains and releases oil like a sponge. Due to time and temperature conditions, the oil release performance may be depleted. When this happens, the grease will wear out.

6、 Bearings may appear suitable, but they may not last.

Bearings are precision products that require complex manufacturing processes. The use of inferior steel and poor heat treatment can lead to premature wear and peeling of inferior bearings. Poor quality steel may contain hard or soft metal inclusions that may lead to premature failure. In summary, cheap bearings may look the same as high-quality bearings, but it is precisely what you cannot see that makes a difference between a resurgence and a satisfied customer.

In addition, some cheaper wheel hub units use smaller bearing sizes than OEM expectations. This may also lead to premature failure. Unfortunately, the only way to determine is to destroy the new bearing.

7、 The cost of sealing the drive when losing lubrication is much lower than that of damaged components.

The most important maintenance technique on repairable bearings is to invest in a good set of sealed drives. Even slight deformation of the seal during installation can shorten the lifespan of internal bearings. Some people may ask, "Why can't I use an impact wrench to secure the shaft nut?" Although using an impact wrench may seem easier, it is not recommended to do so.

During disassembly, the impact wrench can damage the shaft nut threads and impact the CV joint. When adjusting nuts or bolts that may have insufficient or excessive torque, it can also create an incorrect sense of safety. This can make the hub assembly prone to failure. In addition, in almost all cases, it is best to use new shaft nuts. Some shaft nuts cannot be adjusted and are designed to only be used once.

8、 Follow torque and service information.

Always check service information to understand the correct program. Overtightening adjustable tapered roller bearings is a common error that can lead to premature failure. The tapered roller bearings at the front of RWD vehicles are never preloaded. Their weight does not exceed 15 to 20 foot pounds. The torque when rotating the wheels to ensure that the bearings are in place. Then, loosen the adjusting nut by 1/6 to 1/4 turn and lock it in place with a new cotter pin. As a rule, the end play should be approximately 0.001 to 0.005 inches.

9、 The design of bearings is constantly changing.

For engineers, the design and selection of wheel bearings can be a balance between durability, cost, and fuel economy. Large bearings may be very suitable for combating potholes and heavy loads, but there is only so much space in the wheels and steering knuckles. Due to the larger sealing surface, larger bearings may also have increased rolling resistance. On the other hand, if the diameter of the bearing is too small, it may not be able to withstand the load and may not have enough space to place the shaft. Smaller wheels may also lack the stiffness to control flange and rotor motion.

Axial spline hub or face spline hub is changing the way the shaft is connected to the hub and rotor. Asymmetric hub bearings allow larger wheel and tire components to be installed on vehicles with additional weight or rolling resistance. Both technologies have new service programs, and you should be familiar with these programs.