- Wheel bearing
- Wheel bearing with ABS magnetic ring
- Defects and malfunctions
A wheel bearing allows the wheel to rotate on its axis. The wheel bearing provides a smooth transmission of movement between the wheels drive shaft and the rocket. Properly functioning wheel bearings ensure that the wheels can turn with as little resistance as possible.
Wheel bearings are usually designed as angular contact bearings, deep groove ball bearings or tapered roller bearings (tapered roller bearings). The different types of bearings are shown on the page bearings described.
The wheel bearing in the picture below is pressed into the knuckle. The hub is pressed into the inner ring of the wheel bearing. The wheel bearing thus connects the rotating hub to the knuckle. The drive shaft transfers power from the transmission to the wheel. The CV-joint outer splines are slid into the hub inner splines. The drive forces from the drive shaft are passed on to the hub, where the brake disc and wheel are attached.
To replace the bearing, the hub must be pressed out of the inside of the bearing. A bearing puller or hammer puller can also be used to remove the hub. The bearing will always be damaged, so it must always be replaced after disassembly. When the hub has been removed from the bearing, the bearing must be pressed out of the knuckle. The image below shows an overview of the mounting of the bearing and the hub. The locknut is screwed onto the shaft and ensures that the bearing is mounted under preload.
In the picture below, the hub is pulled out of the bearing with a hammer puller.
The remaining bearing can be pressed out of the hub with a pressing tool. In almost all cases, the inner ring of the old bearing is still on the hub. When the old hub is mounted again, this ring must still be ground off or hammered. There is a chance that the hub will be damaged if it is not done professionally.
Not all wheel bearings need or can be pressed. There are also so-called cassettes, which are screwed onto the steering knuckle as a whole with bolts. Examples of this can be seen in the images below.
To replace this type of wheel bearing, with a driven axle, the drive axle must be removed (attached with the bolt with the blue arrow in the image below left) and the bolts from the knuckle must be removed (indicated by the two red arrows). These are often four bolts.
Wheel bearing with ABS magnetic ring:
Nowadays, the magnetic ring of the ABS often integrated into the wheel bearing. In that case there is no longer a sprocket that is normally mounted against the hub. A magneto-resistive sensor (MRE sensor), or a Hall sensor, registers the speed of the wheel because the magnets in the magnetic ring move past the sensor. This ABS sensor sends a block signal to the ABS control unit based on the speed of the magnetic ring.
Compared to the ABS system with inductive sensor and sprocket, this system offers the advantage that the speed is measured from 0 km/h as opposed to 5 km/h with the inductive sensor. This system therefore already works at lower vehicle speeds.
Replacing such a wheel bearing is more complex than with a bearing without a built-in magnetic ring. The magnetic ring must of course not be damaged during installation, but you must also pay attention to the mounting direction. The bearing can often be mounted in two ways. Sometimes the mistake is made to mount the bearing the other way around, so that the magnetic ring is on the side of the brake disc. In that case, the bearing will have to be expanded again. The bearing will fail again and a new bearing will have to be used again.
To check whether the magnetic ring is on the right side, there are special magnetic cards that can be held against the wheel bearing (see picture).
Defects and malfunctions:
Wheel bearings can fail for several reasons:
- old age
- Driving against curbs
- Too little grease due to incorrect assembly or a leaking seal
- Sporty driving behaviour
- Driving through industrial areas where iron ore is located and iron swarf can end up in the bearing
A defective wheel bearing can be recognized by a buzzing sound that increases at higher vehicle speeds. The buzzing sound should not be confused with cupped tires. The sound with a defective wheel bearing often changes when cornering. For example, if a wheel bearing on the left side of the vehicle is defective, the noise will be louder if the left wheels are loaded more. That happens when steering to the right; this creates more lateral forces and weights on the left wheels. When steering to the left, the right wheels will be loaded more, so that the noise is less. If the sound does not change when turning left or right, there is a greater chance that there is cupping on the tires.
In the video, the sound of a defective wheel bearing can be clearly heard.
Another defect that can occur in wheel bearings is play. The play can be felt by jacking up the wheel, gripping the tire by the sidewalls and rocking it back and forth (see picture).