Car wheel bearings do not use oil, but grease, often called "butter." Mineral oil is usually used as the base oil of grease, but when special properties such as low-temperature fluidity and high-temperature stability are required, synthetic diester oils, silicone oils, polyethylene glycol oils, lubricating oils, etc. are required.
Low viscosity base oil greases are suitable for low temperature and high speed applications, while high viscosity base oil greases are suitable for high temperature and high load applications. In fact, any bearing needs "butter", and the bearing will generate high heat when running at high speed. If the heat reaches a certain value, the bearing will be damaged. The only way to reduce heat is to have adequate lubrication.
The better the lubrication, the smoother the bearing movement, the smaller the friction and the lower the heat. The durability of bearings depends entirely on the degree of lubrication. In everyday vehicle breakdowns, 9 out of 10 disc bearings are damaged due to lack of lubrication. The maintenance cycle of truck hub bearings is about 30,000km.
Previous model wheel bearings were prone to damage because the ball bearings used were not fully sealed and relied on lubricant to resist wear. It won't take tens of thousands of kilometers to clean up, beyond repair. Uses a direct replacement method so there is no re-applying of lubricant.
At present, tapered bearings and bearing units are widely used in automobiles and have developed to four generations. This method can effectively disperse the axial force caused by wheel impact, but there is also lubricating oil, but it does not need to be used regularly. Various rolling machinery parts are inseparable from bearings, so bearing maintenance and lubricating oil filling are also common.
But in life, we rarely see bearing repairs on cars, so we have this problem. The reason automotive wheel bearings require no maintenance is by design. If the bearing is sufficiently sealed to block external foreign matter, the benefits of long-term lubricating oil can be exerted.
As long as there is lubricating oil, the bearings will not be damaged. Therefore, at the beginning of the design, the automotive bearings considered the issue of future maintenance and adopted maintenance-free bearings. Wheel bearings on cars are maintenance-free. Maintenance-free is not the absence of lubricating oil, but the sealing of lubricating oil in the bearing.
Under normal use, damage may not occur until the vehicle is scrapped, so there is naturally no need for refueling and maintenance. Wheel bearings are sealed so grease from the inside can't escape and dirt from the outside can't get in. As long as the grease cannot flow out, it will not be lost. Its function is simple lubrication, and there is no problem of malfunction or failure.
Therefore, the four wheels usually do not need lubrication. As long as there are no abnormalities, there is no need for lifelong maintenance. If a bearing is found to be leaking grease, it needs to be repaired. Normal, no damage. It’s okay to drive your car until it’s scrapped. If the bearing is damaged, you will hear abnormal sounds when driving the vehicle because the steel balls in the bearing cannot work properly and the friction will make the sound.
It's broken and just needs to be replaced. In some vehicles, the bearings are connected to ABS sensors. If it breaks, you need to replace it. The price will also be more expensive. Car wheel bearings usually have a long service life, and most of them can be used for more than 100,000 kilometers. Some cars have traveled hundreds of thousands of kilometers and remained undamaged throughout their lives.
Most cars where bearings are commonly replaced are older cars. Bearings do not require maintenance, so their service life is not only related to their own quality issues, but also to the vehicle's use environment. Harsh driving conditions, excessive bumps, no deceleration on speed bump pits, heavy vehicle loads, frequent full loads or overloads, etc., will affect the service life of the bearings.
These road conditions and usage methods will not only affect the service life of the bearings, but also the service life of the shock absorbers, tires and other chassis parts. Therefore, where the speed should be reduced, the speed must be reduced without overloading. When oil leakage from the wheel shaft or abnormal noise from the driving wheel bearing is found, it must be replaced in time.
Because when the bearing is damaged, it will increase the driving resistance and consume more oil. In severe cases, the wheel mechanism will be damaged, causing the wheel hub to fall off, affecting driving safety. The bearings of household cars are basically maintenance-free and we do not need to maintain them every day. One more thing to say is that the 4S shop or repair shop has a repair kit called a brake repair kit.
There is a bottle of grease inside, specifically for the bearing flange. This kind of grease can not only avoid direct engagement between the steel ring and the flange, but also has the characteristics of high temperature resistance. This is said to be to further protect the wheel bearings. Avoiding bites is obvious, but whether it actually protects the bearings is less clear.
