What material is the rear wheel bearing of a car made of
The material of the rear wheel bearings of vehicles is usually high-carbon chromium bearing steel (such as GCr15), which has high hardness (58-65HRC) and good wear resistance, and is suitable for the manufacturing of traditional rear wheel bearings of automobiles.
Material selection under special working conditions
In high-temperature or corrosive environments, the following special materials may be used:
Youdaoplaceholder0 High-temperature working conditions : When the temperature exceeds 180℃, cobalt-based alloys, chromium-based alloys or molybdenum-based alloys should be used.
Youdaoplaceholder0 Corrosive environment : Use martensitic stainless steel (corrosion-resistant and with high hardness) or austenitic stainless steel (with better corrosion resistance).
Traditional manufacturing process
The rear wheel bearings of traditional automobiles mostly adopt a combination structure of double-row tapered roller bearings or ball bearings. Their installation, oiling, sealing and clearance adjustment are all completed on the automotive production line.
High-performance sealing ring
Due to the fact that hub bearings are very close to the ground and parts such as brake discs with high temperatures, they need to adapt to various complex road conditions and harsh driving environments. Therefore, the bearing sealing ring must have excellent grease leakage prevention performance, and at the same time, it must also have good heat resistance, mud and sewage prevention performance.
Rolling technology
The third-generation hub bearings generally adopt the rolling technology to self-lock the half inner ring. When the rolling technology is used, the axial load causes plastic deformation at the end of the hub main shaft, thus connecting the hub main shaft and the half inner ring as one. Compared with the traditional nut fastening, the third-generation hub bearing that adopts the rolling technology helps to reduce volume and weight, lower costs, and improve the reliability of the hub bearing. At the same time, when assembling it into a car, the step of adjusting the positions of internal components is eliminated.
Lightweight and miniaturized
When designing the structure of the second and third generation hub bearings, finite element analysis must be carried out to ensure that the flange has sufficient rigidity while minimizing its volume and weight as much as possible. Among them, the rigidity of the third-generation hub bearing refers to the inclination Angle of the hub flange relative to the outer ring flange. The weight of the axle is reduced through integrated and miniaturized design. The second-generation hub bearing is 180g lighter than the first generation, and the third-generation hub bearing further reduces the weight by 120g.
Low friction torque
An important measure to reduce the fuel consumption of automobiles is to design hub bearings with low friction torque. The main factors affecting the friction torque of bearings are the type of bearings and the preload. The sealing of bearings accounts for a large proportion of the friction torque components. Therefore, improving the sealing design to reduce the frictional torque can significantly enhance the performance of hub bearings. Hub bearings have evolved from the first generation to the latest fourth generation, with the frictional torque significantly and gradually decreasing.
ABS technology
ABS is an automotive safety control device with advantages such as anti-slip and anti-lock. When a car brakes suddenly, it automatically adjusts the braking force by detecting the wheel speed to prevent the wheels from locking up and shorten the braking distance. The detection of rotational speed is carried out by magnetic sensors installed on the parts that rotate with the wheels and nearby fixed on the vehicle body. There are two types of hub units with ABS sensors: one is placed inside the hub, while the sensors are installed on other parts; Another type is placed inside the hub together with the sensor (referred to as the hub unit with sensor).
Worn or damaged hub bearings or hub units can cause inappropriate and costly failures of your vehicle during driving, and even pose a threat to your safety. Please pay attention to the following matters when using and installing hub bearings:
To ensure safety and reliability to the greatest extent, it is recommended that you frequently inspect the hub bearings regardless of the vehicle's age - pay attention to early warning signs of bearing wear: including any friction noise during rotation or abnormal deceleration of the suspension combination wheels when turning.
For rear-wheel drive vehicles, it is recommended that the front hub bearings be lubricated when the vehicle has traveled 38,000 kilometers. When replacing the braking system, check the bearings and replace the oil seals.
If you hear an abnormal noise coming from the hub bearing area, the first and most important thing is to find the location where the noise occurs. There are many moving parts that may produce noise, or it could be that some rotating parts have come into contact with non-rotating parts. If it is confirmed that the noise is from the bearing, the bearing may be damaged and needs to be replaced.
Because the working conditions that cause the failure of the bearings on both sides due to the front wheel hub are similar, it is recommended to replace them in pairs even if only one bearing is damaged.
Hub bearings are rather sensitive, and in any case, the correct methods and appropriate tools must be adopted. During storage, transportation and installation, the components of the bearing must not be damaged. Some bearings require a relatively large pressure to be pressed in, so special tools are needed. Be sure to refer to the car manufacturing manual.
When installing bearings, they should be done in a clean and tidy environment. Fine particles entering the bearings will also shorten their service life. It is very important to maintain a clean environment when replacing bearings. It is not allowed to strike the bearing with a hammer. Be careful not to drop the bearing on the ground (or handle it improperly in a similar way). Before installation, the condition of the shaft and bearing housing should also be inspected. Even slight wear can lead to poor fit, thereby causing premature failure of the bearing.
For hub bearing units, do not attempt to disassemble the hub bearings or adjust the sealing rings of the hub units; otherwise, the sealing rings may be damaged, allowing water or dust to enter. Even the raceways of the sealing ring and the inner ring were damaged, resulting in the permanent failure of the bearing.
There is a magnetic thrust ring inside the sealing ring of the bearing equipped with the ABS device. This thrust ring must not be subject to collision, impact or contact with other magnetic fields. Before installation, remove them from the packaging box and keep them away from magnetic fields, such as the electric motors or power tools in use, etc. When installing these bearings, observe the ABS alarm needle on the dashboard through road condition tests to adjust the operation of the bearings.
For hub bearings equipped with ABS magnetic thrust rings, to determine which side the thrust ring is installed on, you can bring a small and light object close to the edge of the bearing. The magnetic force generated by the bearing will attract it. When installing, point the side with the magnetic thrust ring inward, directly facing the sensitive components of the ABS. Incorrect installation may lead to the failure of the braking system's function.
Many bearings are sealed and do not require grease throughout their entire service life. Other unsealed bearings, such as double-row tapered roller bearings, must be lubricated with grease during installation. Due to the different sizes of the inner cavities of the bearings, it is difficult to determine how much grease to add. The most important thing is to ensure that there is grease in the bearings. If there is too much grease, when the bearings rotate, the excess grease will seep out. General experience: During installation, the total amount of grease should account for 50% of the bearing clearance.
When installing lock nuts, the magnitude of the torque varies greatly due to the differences in bearing types and bearing housings. Please refer to the relevant instructions.
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