How much do you know about rear axle bearing?

Rear axle bearing are parts that connect tires (rotating parts)/brake discs (rotating parts) and steering knuckles (Knuckles, fixed parts). Its main function is to reduce friction for the rotating pair, while also transmitting force. It bears very large radial loads (vehicle weight) and axial loads (lateral force or lateral impact force of tires during steering).

Rear axle bearing are divided into ball bearings and tapered roller bearings.
The main difference lies in whether the shape of the rolling medium (roller) inside is spherical or conical.
Unless it is a particularly heavy-duty vehicle (such as construction vehicles, large SUVs, pickups, etc.), the rear axle bearing of passenger cars are generally ball bearings.

Rear axle bearing strength:
Because bearings have to withstand very large radial and axial loads, strength is crucial. Generally, stress and strain analysis is conducted through CAE, with a certain safety margin added.

Rear axle bearing stiffness:
If the stiffness of the bearing is poor, it will cause significant deformation of the flange surface connecting the bearing and the brake disc when the bearing is subjected to lateral force, resulting in problems such as uneven wear of the friction plate.

Rear axle bearing drag torque:
The drag torque of the bearing refers to the resistance when the bearing rotates, and its magnitude affects fuel consumption, which in turn affects the range of new energy vehicles.

Rear axle bearing lifespan:
Bearings are maintenance free throughout the entire lifecycle of a vehicle, so their lifespan must be longer than that of the entire vehicle. There are very complex calculation formulas for its lifespan, which is also the know-how of different component suppliers.

Rear axle bearing sealing performance:
It refers to the sealing ring preventing external water/dust from entering the interior of the bearing, thereby affecting the lubrication effect of the steel ball and ultimately affecting its lifespan.

How to maintenance rear axle bearing？
Remove the decorative cover and dust cover of the wheel hub and axle head;
Scrape off the old lubricating grease from the bearings, shaft necks, and hub cavities, clean the hub bearings and shaft necks with a cleaning agent and wipe them dry with a cloth, and finally wipe the hub cavities clean with a cloth;
Use specialized tools to remove the wheel hub;
Check the rear axle bearing and bearing races
If pitting is found on the bearing seat ring, the bearing parts of the Sully air compressor should also be replaced. If cracks, fatigue peeling, and loose bearing rollers are found, the bearing should be replaced.
Check the fit between the inner diameter of the bearing and the journal
When measuring the shaft neck with a clearance of no more than 0.1Omm, measurements should be taken at the upper and lower parts perpendicular to the ground. If the fit clearance exceeds the specified usage limit, it is not allowed to reduce the clearance by burrs or pockmarks on the shaft neck. The bearing should be replaced to restore the normal fit clearance.

After all parts meet the requirements, apply lubricating grease to the inner bearing and place it in the wheel hub.
Apply a thin layer of lubricating grease in the hub cavity and shaft head cover to prevent rust. Be careful not to apply too much lubricating grease in the hub cavity, otherwise it will affect heat dissipation and braking. The lubricating grease should be squeezed into the bearing until it emerges from the other side of the bearing.
Install the wheel hub and outer bearing back onto the shaft neck, manually tighten the shaft head adjustment nut, and then use a shaft head wrench to tighten the adjustment nut to the specified torque. After tightening the nut, rotate the wheel hub left and right a few times to check the installation of the bearing; On the other hand, the correct fit between the bearing and the seat ring is achieved through rotation. At this point, the bearing tightness is appropriate, and the wheel can rotate freely without feeling any axial clearance.

Install the locking plate, fixing nut, tire, dust cover, and decorative cover in sequence.
After adjusting the wheel hub bearings, drive for a distance of about 10km, stop and check to wipe the temperature of the wheel hub. If it heats up, it is caused by the bearings being adjusted too tightly, and should be readjusted by appropriately relaxing the bearing tightness.