Hub bearing

The main role of hub bearings is to bear weight and provide accurate guidance for the rotation of the hub, it bears axial and radial loads, is a very important part. The traditional automobile 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 the automobile production plant, high cost, poor reliability, and the maintenance of the car in the repair point, the bearing needs to be cleaned, oiled and adjusted. Wheel hub bearing unit is developed on the basis of standard angular contact ball bearings and tapered roller bearings, it integrates the two sets of bearings into a whole, featuring good assembly performance, omitted clearance adjustment, light weight, compact structure, large load capacity, and high efficiency by preloaded grease for sealed bearings, omitted outer hub seal and free from maintenance, etc., it has been widely used in cars and gradually expanded in heavy trucks

Car hub bearing s used to be mostly used hub in pairs mounting single row tapered roller or ball bearing. As the development of technology, hub unit has been widely used in cars. The using range and usage amount of hub bearing units are increasing day by day, and have now developed to the third generation: the first generation is composed of double-row angular contact bearings. The second generation is the outer ring with a flange for fixing the bearing. So the bearing can be simply fixed to the axle with nuts ，makes you easy for maintenance. The third generation of the hub bearing adopts bearing unit and anti-lock brake system ABS. The hub unit is designed to mount with an inner flange and an outer flange. The inner flange is bolted to the drive shaft, and the outer flange is attached to the whole unit to the bearing. Because of Worn or damaged hub bearings or hub units can cause your vehicle to travel inappropriately and costly failure, or even harm to your safety. Please pay attention to the following in the use and installation of hub bearings:

1. For maximum safety and reliability, it is recommended that you check the hub bearings frequently, anyhow about the age of the vehicle -- pay attention to the bearing for early warning signs of wear, including any friction noise during rotation or abnormal deceleration of the suspension assembly wheel during turning.

For rear-wheel drive vehicles, it is recommended that the front hub bearings should be lubricated before the vehicle travels up to 38,000km.When the brake system is replaced, check the bearings and replace the oil seals.

2.if there is any noise heard of the hub bearing part, first of all, it is important to find the location of the noise. There are many moving parts that may produce noise, and it is possible that some rotating parts may come into contact with non-rotating parts. If the noise is confirmed in the bearing, the bearing may be damaged and needs to be replaced.

3. Because of both bearings in a car are similar to the working conditions due to the failure of the front hub, even if only one bearing is broken, it is recommended to replace the bearing in pairs. 

4.Hub bearings are sensitive to assembly, the right approach and right tools are needed in any case. Bearing parts shall not be damaged during storage, transportation and installation. Some bearings require a high pressure fit, so special tools are needed. Be sure to refer to the car manufacturer's instructions .                                                                                                     

5.The bearing should be installed in a clean and tidy environment, any small particles into the bearing will shorten the service life of the bearing. It is important to maintain a clean environment when replacing bearings. Bearing is not allowed to be struck with a hammer. Do not drop the bearing on the ground (or dispose of it improperly).The condition of the shaft and bearing pedestal should also be checked before installation. Even minor wear and tear can lead to poor fit and 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 will be damaged and water or dust will enter. Even the raceway of the seal and inner ring are damaged, resulting in permanent bearing fail.

7. There is a magnetic thrust ring in the seal ring fitted with the bearing of ABS device. The thrust ring cannot be touched, impacted or collide 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. While these bearings are installed, the operation of the bearings can be changed by observing the ABS alarm needle on the instrument panel through a road test.

8. For the hub bearing equipped with ABS magnetic thrust ring, in order to determine which side the thrust ring is mounted on, a light "iron plate" can be used to be close to the edge of the bearing, and the magnetic force generated by the bearing will attract it. The side of the magnetic thrust ring should be  pointed inward .during installation, face to the sensitive element of ABS.

Note: Improper installation may result in failure of the braking system.

9. Many mounting bearings are sealed and do not add grease throughout their life. Other unsealed bearings，such as double row tapered roller bearings require to be lubricated during installation. It is difficult to determine how much grease to be added due to the different size of the inner cavity of the bearing. The most important thing is to ensure that there is grease in the bearing. If there is too much grease, when the bearing rotates, the excess grease will leak out. As a general rule of thumb: during installation, the total amount of grease should account for 50% of the clearance of the bearing.

10. Due to the bearing type and bearing housing, the size of the torque varies greatly as the lock nut installing. Refer to the instructions.

How to repair and maintain hub bearings

Hub bearing is an important moving part of automobile. Hub bearings are responsible for reducing the friction resistance of chassis operation and maintaining the normal running of the car. If the hub bearing is out of order, it may cause noise, bearing heating and other phenomena, especially the front wheel is more obvious, easy to lead to direction loss control and other dangerous phenomena.  Therefore, hub bearings must be maintained on schedule. 

1. Inspection of the Hub bearing

(1) When the tightness of the hub bearing is checked, first of all is to support the axle of the wheel at one end of the hub, then set up the car safely with tools such as supporting stool and masking wood.

(2) Turn on the tested wheel several times by hand to check whether the rotation smooth and any abnormal noise. If the rotation is unstable and a friction sound, the braking part is not normal. If there is no noise, the rotation is uneven and loose, the bearing part is abnormal. The hub should be disassembled when the above abnormal phenomenon occurs. For small cars, when hub bearings are checked, hold the top and bottom sides of the tire with both hands, pull the tire back and forth with both hands, and repeat many times. If normal, there should be no feeling of looseness or blockage; if swing, and a clear feeling of looseness, should disassemble the hub.

(3) Check on braking. Usually in the inspection of the hub bearing, accompanied by the inspection of the wheel brake device, if there is an oil mark inside the tire, it is likely to be caused by the brake pump or brake pipe oil leakage, should promptly found out the cause, and ruled it out.

2. Maintenance of hub bearings

Before removing the hub, the hub should be prepared for maintenance, and the car should be stopped and set up the bridge to ensure the safety of maintenance.

(1) Remove the decorative cover and dustproof cover of the hub shaft head;

(2) Remove the tire nut and tire, and be careful not to damage the thread of the tire bolt. If it is a disc brake, the brake should be removed, and then remove the lock ring or lock pin with clamp.

(3) remove the hub with a special tool;

(4) Scrape off the old grease from the bearings, journal and hub cavities, clean the hub bearings with a cleaning agent, then dry up the bearings and journal with a cloth, and finally wipe the hub cavities cleanly.

(5) Check the hub bearing and housing, if any cracks, fatigue spalling and loose rollers are found the bearing should be replaced, also pitting points are found on the bearing ring, must be replaced.

(6) Check the fit between bearing inner diameter and journal. The fit clearance shall not be greater than 0.1Omm. When measuring journal, it shall be measured at the upper and lower parts of the vertical ground (where is the most worn part).If the fit clearance exceeds the specified use limit, the bearing shall be replaced to restore the normal fit clearance. No burr and pitting on the journal is allowed.，so that to narrow the gap. 

(7) After all parts meet the requirements, grease the inner bearing and put it into the hub.

(8) Being grease applied to the inner cavity of the bearing, it shall be squeezed into the bearing until it comes out from the other side of the bearing.  

 (9) Mount the hub and the external bearing back on the journal by screwing the adjusting nut, and tighten the adjusting nut with the shaft head wrench according to the specified torque. After that, turn the hub several times to check the bearing is installation. On the other hand, turn the hub to check whether the bearing and seat ring are properly matched. Check whether the bearing tightness is appropriate at this time, so that the wheel free rotation without feeling the axial clearance

 (10) Finally, install the lock piece, fixing nut, tire, dust cover and decorative cover in turn.

(11) After the hub bearing has been adjusted, drive a certain mileage (about 1Okm), and stop for inspection by touching the hub's temperature. If it is heat, it must be caused by tight mounting bearing, and the bearing tightness should be adjusted again to fit properly.

In the process of maintenance, it is often found that some cars have a large driving noise, check the tire abnormal wear, no obvious abnormal sound in the lifting wheel rotation. This phenomenon is often caused by the abnormal damage of the hub bearing; the so-called abnormal damage refers to the bearing damage caused by improper installation. The front wheel bearing of a car is generally a double row ball bearing. If you use a hammer to hit the bearing as installing the bearing, or if you put the bearing into the bearing seat by squeezing the bearing inner ring, it will cause damage to one side raceway. of the bearing When the vehicle is moving, can make noise, and when the wheel is off the ground, there is no obvious noise due to the better side of the raceway supporting. Proper mounting operation is the key to long bearing life.

The hub bearing unit with ABS sensor mainly comprises a flange, a rotating body of tooth ring, a seal assembly and a wheel hub. An ABS sensor is arranged on the wheel hub. The magnetic steel in the ABS sensor is arranged on the rotating body of tooth ring and is coordinated with tooth ring; it is fixedly connected with the flange. The ABS sensor mainly includes a shell, magnetic steel and a coil. The magnetic steel is arranged on the rotating body of the tooth ring, and the magnetic steel is in coordination with the rotating body of the tooth ring. The coil is connected to the plug by a signal wire. The tooth ring of rotating body is splined with the flange. The end face of the flange is provided with holes matched with bolts, which can be directly connected with suspension, brake devices and tires. The inner hole of the flange plate is provided with a spline keyway, which can be used in conjunction with the constant speed driving shaft. The beneficial effect of the utility model is that this structure replaces the original combination of automobile steering knuckles, wheel hubs and bearings, which not only integrates the functions of the three as a whole, but also greatly reduces the volume and weight of the original structure and greatly improves the reliability.