A hub bearing assembly is an important part of every wheel assembly. It enables wheels to turn and it is also important for vehicle safety and handling. A hub bearing assembly is a critical component when it comes to performance, ride smoothness and even fuel efficiency whilst they also play a big role with ABS (anti-lock braking systems). They are located in the middle of the wheel hub assembly which is basically the part that attaches the wheel to the vehicle.
Wheel Bearing vs Hub Bearing
While both hub and wheel bearings both house bearing spheres, which are lubricated to allow the wheel to rotate, they do differentiate when it comes to the way they are assembled. A hub bearing comes as a complete unit from the manufacturer’s factory whilst wheel bearings can be taken apart for lubrication and repairs.
Excessive wear on the cone bore comes in the form of ridges and discolouration. In this case, the hub barrel is replaced since there is irreversible damage on the barrel surface. This is usually caused from loss of axle retention and wear which can be the case of another issue called, loss of bearing retention.
Loss of Bearing Retention
When you feel a wheel vibrating or excessive noise coming from it, it means that the axle-retaining nuts are worn out and have started to move due to the loss of bearing retention. This makes the axle-retaining nut to back off and provide improper torque which can cause misalignment and wear. This is solved by tightening the new axle-retaining nut to the proper torque level to avoid it from happening in the near future.
Sharp objects can damage or pinch the sensor cable which will cause it to turn the ABS light on. ABS malfunction can also be the result of a broken wheel speed sensor and sometimes a crack in the cable or a loose cable too. To ensure this doesn’t happen, a mechanic should route the entire cable through a retaining clip and put a hub that’s in good shape to reduce wear.
Humming & Rumbling
While these noises are mainly the result of faulty electrical or drivetrain components they can also be associated with the hub bearing. If you hear humming and rumbling noises when driving in a straight line and hear the same noises intensify when you turn either to the left or right then you can be sure that the issue is hub-related.
Grinding is usually the result of mechanical damage on a wheel-end system but when it is associated with the wheel hubs or wheel hub bearing it usually happens when turning or when there is a shift in weight. Grinding occurs when there is a loss of integrity either from a roller or raceway damage.
Vibration & Wobble
When wobbling and vibration are not related to a worn out or damaged tire or with severe misalignment of the chassis it can mean that there is a loss of clamp with the hub or bearing. This could also be the result of a bearing with severe mechanical damage and it can occur when the lug nuts are not tightened at the proper torque level.
What Causes These Issues
Hitting or even sliding into curbs or other objects can cause rims to bend, tires to wear out or get punctured and also damage to the bearings. Whilst bearing damage won’t occur straight away, if done enough times you’ll eventually feel or hear the consequences whilst driving. This can also brake or damage tie rods, control arms, struts and strut mounts.
In case you do happen to hit your car into a curb, go to the mechanic as soon as possible to have your vehicle inspected. This will save you money in the long run if something was to be damaged. You should avoid driving over speed bumps or through potholes at high speeds. Sometimes they are inevitable but you should treat potholes the same as speed bumps and drive carefully over them.
Driving through potholes or generally poorly made roads is going to treat the whole wheel assembly badly including the wheel hub bearing. Again, although this won’t happen immediately after your first time driving on a bad road it will present itself further down the line. So avoid driving on poor roads as much as you can.
In case you’ve had a new bearing installed with the old nuts, bolts, circlips or seals expect to have the bearing failing or under performing. If your mechanic hasn’t used the right tools for the job then it’s very likely that the exterior or interior of the bearing (or both) have been damaged.
If you have fitted bigger or wider rims, tires, or tires with lower thread walls you’ve definitely added a lot of weight on the bearing which makes it wear out quicker. Stiffer shocks, suspension grips and absorbers can also accelerate wear which is why it’s best to have rims, tires, shocks and springs that are specified by the manufacturer.