Automotive wheel bearings

March 12, 2020

Automotive wheel bearings

The main function of a hub bearing is to support the load and provide precise guidance for the rotation of the hub. It bears both axial and radial loads and is a very important component. Traditional automotive wheel bearings are composed of two sets of tapered roller bearings or ball bearings. The installation, oiling, sealing and clearance adjustment of the bearings are carried out on the automobile production line. This structure makes it difficult to assemble in a car production plant, with high cost and poor reliability, and when the car is maintained at a repair point, the bearing needs to be cleaned, oiled and adjusted. The hub bearing unit is developed on the basis of standard angular contact ball bearings and tapered roller bearings. It integrates two sets of bearings, has good assembly performance, can eliminate clearance adjustment, light weight, compact structure, and load capacity. Large, sealed bearings can be pre-installed with grease, omitting the external hub seal and maintenance-free, etc., has been widely used in cars, there is also a trend of gradually expanding the application in trucks.
Chinese name
Automotive wheel bearings
Foreign name
hub bearing
Pay attention
Proper installation operation can extend bearing life
main role
Load-bearing and precise guidance for wheel rotation

Installation and use

In the past, wheel hub bearings for cars have used single-row tapered roller or ball bearings in pairs. With the development of technology, cars have widely used car wheel units. The use range and quantity of hub bearing units are increasing day by day. Now it has developed to the third generation: the first generation consists of double row angular contact bearings. The second generation has a flange for fixing the bearing on the outer raceway. The bearing can be simply sleeved on the wheel shaft and fixed with a nut. Makes car maintenance easier. The third-generation hub bearing unit uses a bearing unit and an anti-lock brake system ABS. The hub unit is designed with an inner flange and an outer flange. The inner flange is bolted to the drive shaft. The outer flange installs the entire bearing together. Worn or damaged hub bearings or hub units can make your vehicle unsuitable and costly to fail on the road, and can even harm your safety .
In the use and installation of hub bearings, please note the following:
1. In order to ensure the maximum safety and reliability, it is recommended that you always check the wheel bearing regardless of the age of the vehicle-pay attention to the early warning signal of wear of the bearing: including any frictional noise during rotation or the suspension combination wheel turning Unusual deceleration. For rear-wheel-drive vehicles, it is recommended to lubricate the front wheel bearings when the vehicle travels up to 38,000 kilometers. When replacing the brake system, check the bearings and replace the oil seal.
2. If you hear noise from the hub bearing, first of all, it is important to find where the noise occurs. There are many moving parts that may generate noise, or some rotating parts are in contact with non-rotating parts. If it is confirmed that it is noise in the bearing, the bearing may be damaged and needs to be replaced.
3. Because the working conditions of bearing failure on both sides caused by the front hub are similar, even if only one bearing is broken, it is recommended to replace them in pairs.
4. Wheel hub bearings are relatively sensitive. In any case, correct methods and suitable tools need to be used. During storage, transportation and installation, the bearing components must not be damaged. Some bearings require a larger pressure to press in, so special tools are required. Be sure to refer to the car manufacturer's instructions.
5. The bearing should be installed in a clean and tidy environment. Fine particles entering the bearing will also shorten the service life of the bearing. It is important to maintain a clean environment when replacing bearings. It is not allowed to hit the bearing with a hammer. Be careful not to drop the bearing on the ground (or similar improper handling). The condition of the shaft and the bearing seat should also be checked before installation. Even minor wear can cause poor fit and cause early failure of the bearing.
6. For the hub bearing unit, do not attempt to disassemble the hub bearing or adjust the seal ring of the hub unit, otherwise the seal ring may be damaged and water or dust may enter. Even the raceways of the seal and the inner ring are damaged, causing permanent failure of the bearing.
7. There is a magnetic thrust ring inside the sealing ring equipped with ABS device bearing. This kind of thrust ring cannot be impacted, impacted or collided with other magnetic fields. Remove them from the box before installation, and keep them away from magnetic fields, such as motors or power tools used. When installing these bearings, observe the ABS alarm pin on the dashboard through road conditions tests to change the operation of the bearings.
8. For hub bearings equipped with ABS magnetic thrust rings, in order to determine which side the thrust rings are mounted on, you can use a small and light object near the edge of the bearing, and the magnetic force generated by the bearing will attract it. During installation, point the side with the magnetic thrust ring inward, facing the sensitive components of the ABS. Note: Improper installation may cause the brake system to fail.
9, many bearings are sealed, this type of bearing does not need to add grease throughout the life cycle. Other non-sealed bearings, such as double-row tapered roller bearings, must be greased during installation. Because the inner cavity of the bearing is different in size, it is difficult to determine how much grease is added. The most important thing is to ensure that there is grease in the bearing. If there is too much grease, excess grease will leak out when the bearing rotates. General experience: During installation, the total amount of grease should account for 50% of the bearing clearance.
10. When installing the lock nut, due to the different bearing types and bearing housings, the torque varies greatly [1] .

Maintenance attention

During the maintenance process, it is often found that some cars have a large driving noise, check the tires for abnormal wear, and there is no obvious abnormal noise when turning the wheels on the lift. This phenomenon is often caused by abnormal damage to the hub bearing. The so-called abnormality refers to bearing damage caused by installation. The front wheel bearing of a car is usually a double-row ball bearing. If a hammer is used to install the bearing, or when the bearing is installed in the bearing seat by pressing the inner ring of the bearing, it will cause the bearing raceway on one side. damage. Noise is generated when the vehicle is driving, and no obvious noise is heard when the wheels are off the ground due to the better side of the raceway. Proper installation operation is the key to long bearing life [2] .

What happens to automobile wheel bearing damage

When one of the four wheel hub bearings of the vehicle is damaged, you will hear a continuous hum in the car while the car is moving. This kind of sound ca n’t tell where it is coming from, and it feels like it is in the whole compartment. It's full of this hum, and the louder the faster the speed. Here's how to judge:  
Method 1: Open the window to see if the sound comes from outside the car;  
Method 2: After increasing the vehicle speed (when there is a large hum), set the gear to neutral to allow the vehicle to coast and observe whether the noise comes from the engine. If the hum does not change during neutral, it is likely that the wheel bearings are defective;  
Method 3: Temporarily stop, get out of the car and check whether the temperature of the axle is normal. The method is: touch the four wheels separately with your hands, and roughly feel whether their temperature is consistent If there is a gap, the front wheel should be higher), if you feel the difference is not too big, you can continue to drive slowly to the pit;  
Method 4: Use a lifter to lift the car (previously release the handbrake and suspend the neutral gear). If there is no lifter, you can use a jack to raise the wheels one by one. The human power can quickly rotate the four wheels. The sound is completely different from other axles. With this method, it is easy to tell which axle is the problem.  
 If you encounter severe damage to the hub bearing, if it has cracks, pits or ablation, it must be replaced. Before installing a new bearing, first apply grease, and then install it in the reverse order. The replaced bearing must be flexible and free of debris and vibration [3] .