What is the wheel hub of a car?

Wheel hubs are an important part of a vehicle’s wheels. They are the connection between the wheel and the suspension. As a result, they play an important role within the mechanism of the wheel.

Wheel hubs are made out of durable metal, and connect to the wheel’s axel. They are an essential part of the wheel bearing, and assist in the turning of a vehicle’s wheels. Without wheel hubs, a vehicle would not be able to operate correctly. This is why it is essential to ensure that they are performing as they should.

What does a wheel hub do?

Wheel hubs are essential because they connect each wheel to the vehicle. While you cannot see them without removing the wheel, the vehicle could not operate without these hubs. The wheel hubs enable the driver of a vehicle to move the wheels and steer.

If they are not working correctly, this is when a driver can have issues with their steering wheel alignment. The wheels can become wobbly if the wheel hubs are not correct, and too much friction is placed on the wheel itself.

What does the wheel hub connect to?

The wheel hub is responsible for connecting a wheel to a vehicle. As a result, it connects to both the wheel and the vehicle itself. The wheel hug connects to the vehicle’s wheel axle, this is located on the brake disc side of the chassis.

The tyres are then connected to the wheel hub assembly with studs. Given the location of the wheel hub assembly being located behind the wheel, you can only see it when the wheel of a vehicle has been removed.

What is a wheel bearing and hub assembly?

The wheel bearing and hub assembly are essentially the same component. When it comes to the mechanics of a vehicle’s wheels, there are a number of different names given to the similar components.

However, there is a slight difference between the both, and this comes down to their assembly. When looking at a wheel bearing, this can be taken apart by a mechanic. This is great because it means that each part can be lubricated to ensure that it works seamlessly.

In contrast to this, the hub bearings cannot be taken apart. If there are any issues with them, they need to be replaced, rather than fixed. These are sent out by the manufacturer.

While they essentially do the same job, the difference lies when there is an issue with the component. The wheel bearing and hub assembly are an essential part of a vehicle, given that they are responsible for connecting and securing the wheel to the vehicle.

How much is a wheel bearing hub assembly?

When it comes to the cost of a wheel bearing hub assembly, there is no set cost. This is standard when it comes to different vehicles because there are different sizes and bearings needed. As a result, the cost will depend on the type of model and vehicle you own.

The price of the wheel bearings is not extortionate. On average, they will set you back around £100. However, the price can be higher or lower than this. When looking at the hub assembly, this is more expensive to replace, especially if you need to purchase more than one. You will be looking at paying around £225-£575.

When you take into consideration how important these components are, it is understandable that they are not the cheapest component to replace. The wheel bearing can be fixed, whereas the hub assembly needs to be replaced, this is why there is a significant jump in the price.

What are the different types of wheel hubs?

It is important to note that there are different types of wheel hubs and bearings, and they can differ depending on the vehicle you own. It is useful to know the differences.

Ball Bearing – Ball bearings are one of the most common types. As the name suggests, they are round balls made out of metal. They are not typically used for wheel hubs because they are not strong enough. However, they can be present in other parts of vehicles.

Straight Roller Bearings – These bearings have a cylindrical shape. They are typically used in gear boxes, and can deal with a heavier-duty job. They can also handle thrust loads.

Tempered Roller Bearings – This type of bearing also has a cylindrical shape, but is tapered on one side. They are particularly durable and heavy duty.

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What Are Hub Units
(Wheel Bearings)?

Structure

In the past, wheels on cars used a combination of two radial ball bearings or tapered roller bearings. With the increasing integration of the wheel bearing and the surrounding components, we have now reached a point where the "3rd generation" of hub units have been put into practical use.

• 1st-generation hub unit

The outer rings of two single-row bearings are integrated with each other, the unit is greased and sealed. There are two types: DAC, which uses balls, and DU, which uses tapered rollers.

DAC type

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DU type

• 2nd-generation hub units

The outer ring of the 1st-generation hub unit is integrated with the flange. These hub units are divided into two types based on which of their rings rotates. In the outer ring rotation type, the wheel is attached directly to the outer ring; this type is only used for the driven wheels. In the inner ring rotation type, the hub shaft is attached to the inner ring; this type is used for both the driving wheels and the driven wheels.

• 3rd-generation hub unit

This is a further development on the 2nd-generation hub unit. These hub units have an integration of the hub shaft and inner ring on the outer side (tire side) of the inner ring rotation type, and the number of 3rd-generation hub units with built-in high-performance sensors is growing. For driven wheels, the method of fastening the hub shaft and inner ring with nuts has been changed to the "shaft end clinching" method.

• Built-in ABS sensors

In order to improve car safety, the installation of an ABS (anti-lock brake system) that controls the brakes has become widespread, and hub units with built-in sensors equipped with a wheel rotation system have been used to reduce the size and weight, in addition to the process being simplified.

Integrated sensor cover

Built-in stick-type sensor

Features

The hub unit is required to have "both lower fuel consumption and superior driving performance," "high reliability," and "high capacity," and these are incorporated into each component.

• • Achieving both lower fuel consumption and superior driving performance, where lower fuel consumption means a reduction in weight and superior driving performance means both strength and rigidity at a high level
• • High reliability, even in severe environments such as driving on muddy roads, is ensured
• • The high-capacity bearing design is enabled by maximizing the use of allowable space

The following diagram shows the features of a hub unit for a driving wheel.

The seals are among the most important components supporting hub unit function and their techinical performance continues to increase in keeping with the evolution of the hub unit. JTEKT's seals ensure low friction torgue and superior muddy water resistance, and they also use a low friction torque seal to contribute to lower fuel consumption.

Structural map of assembly

Outer side (tire side)
Outer seal Inner side (body side)
Inner seal Standard product

Low-torque spec. product

Hub units for passenger vehicles

With passenger vehicles, the 3rd-generation hub units have been put into practical use.
Lots of vehicles use hub units with balls (ball hub units), but some heavy vehicles (SUVs and the like) use hub units that incorporate high-capacity tapered rollers (roller hub units).

Wheel bearings for commercial vehicles

With heavy commercial vehicles, the predominant arrangement continues even today to be combining two tapered roller bearings. By improving the bearing materials and heat treatment, JTEKT is achieving greater reliability for wheel bearings. The DU 1st-generation hub unit, equipped with a tapered roller, is also used.

When replacing the bearings, you should also replace the oil seals for the wheels.

Oil seals for wheels on commercial vehicles and trailers

When replacing the bearings, you should also replace the oil seals for the wheels.