This small part performs a vital function: without a wheel bearing, the wheel simply will not rotate.
- Understanding the design and malfunctions.
- Where is the wheel hub bearing located?
- Design
- Signs of malfunction
- How to replace a wheel hub bearing
- How to extend its service life
- Wheel hub bearing ratings
A wheel bearing is a part designed to ensure the rotation of the wheel. It is part of the wheel assembly. Modern designs are a maintenance-free assembly of two bearings — so-called HUB bearings or HUB hubs.
Where is the wheel hub bearing located？
The part (or parts, if there are two bearings) is located near the wheel, inside the housing, which is called the wheel assembly or simply the hub. The design of the front and rear hubs differs, but the general principle is the same. We discussed this assembly and its functions in detail in a separate article. Today, we will take a closer look at how the bearing itself is constructed and how its main types differ.
Wheel hub bearing construction
Wheel bearings can be divided into two groups: classic (serviced) and HUB bearings. Let’s take a look at the construction of both types.
Classic single-row (serviceable)
As the name suggests, the moving elements (balls or rollers) are arranged in a single row. However, since the hub is an extremely loaded assembly, a single part is not sufficient. Therefore, single-row bearings are installed in pairs, at a certain distance from each other, so that the load is distributed more evenly. Below is an illustration of a typical wheel hub assembly with two single-row bearings.
The dark green colour indicates the swivel joint, lilac indicates the hub, and yellow indicates the CV joint. The parts we are interested in are highlighted in blue — these are the outer housings of two wheel bearings with red rollers inside. Such bearings, in which the rollers are positioned at an angle (for better load resistance), are called radial thrust bearings.
Single-row bearings can be removed, serviced and reinstalled if necessary. They can also be replaced individually. Therefore, detachable hubs with classic bearings are cheaper and easier to repair.
HUB bearings (maintenance-free)
A more modern design involves a single non-removable housing that already contains two rows of balls or rollers inside. This design is called HUB — hub unit bearings — ‘bearings in a single assembly’. Hub bearings are divided into generations (HUB-I, HUB-II, HUB-III) and differ in design nuances, but the general idea is the same: a non-separable, maintenance-free housing filled with factory lubricant.
The advantages of HUB bearings are their ease of installation and removal (a single unit instead of several parts), as well as high fitting accuracy and lower runout. The downside is their high cost and the inability to service the unit on a modest budget.
Signs of wheel hub bearing failure — how to check
A humming or howling noise while driving. This can manifest itself in different ways: after warming up or, conversely, when cold; when turning, in dry weather, etc.
Vibration from the wheel with a worn bearing.
Hub heating. Recognisable by the temperature of the wheel rim, which will be higher than the others. The main thing is not to confuse heating due to the bearing with heating due to a sticking brake.
Play felt by hand when rocking the suspended wheel.
Extraneous noises — crunching, noise, etc.
The car veering off course. This symptom, like the acoustic effects described above, occurs when parts are extremely worn.
Replacing the wheel hub bearing
As always, the priority should be the sequence described in the repair manual for the specific car. In general, the algorithm for replacing wheel bearings is as follows.
1. Remove the decorative wheel cover to access the wheel nut/bolt. While the car is on the ground, pull off the wheel nut/bolt (do not unscrew it).
2. Raise the vehicle with a jack, remove the wheel and dismantle the brake system components: caliper with disc or brake drum.
3. Completely unscrew the wheel nut/bolt. Next, unscrew (if present) the lock washer, lock nut and other components that secure the hub to the suspension.
4. Remove the hub assembly. In some cases, it is also necessary to unscrew its housing from the suspension component on the inside.
Next, a special puller may be required to press out and replace the bearings separately. If it is a hub bearing, the entire assembly must be replaced.
When reassembling, it is necessary to strictly follow the algorithms prescribed in the manual, as well as to control the work with threaded connections using a torque wrench. Otherwise, there is a high probability of under-tightening or, conversely, over-tightening the wheel bearings, which will lead to their rapid wear and failure.
How to extend the service life of a wheel hub bearing
When installed correctly, modern HUB bearings (and most of them today) do not require any monitoring or maintenance throughout their entire service life. As for the “classics,” the instructions in the operating manual should be followed. If the wheel assembly requires regular attention, such procedures and their frequency will be specified in the documentation. This usually involves periodic tightness checks and disassembly of the hub to check and lubricate the bearings.
Wheel hub bearing ratings
Here is a list of the most reputable brands that manufacture wheel hub bearings.
- SKF. A well-known Swedish brand specializing in bearings.
- Koyo. A Japanese company that manufactures all types of bearings.
- SNR. A French supplier of bearings, including for the assembly lines of various car manufacturers.
- NSK. Another Japanese manufacturer that supplies bearings directly to factories.
- FAG. A well-known German bearing manufacturer.
Brief summary
- Purpose: The wheel hub bearing is a key component that enables the rotation of the vehicle’s wheels.
- Location: Located inside the wheel assembly near each wheel.
- Types of design: There are two main types: classic serviceable bearings and modern maintenance-free HUB bearings.
- Classic bearings: Removable, repairable, usually installed in pairs. Require maintenance and adjustment.
- HUB bearings: Non-removable single assembly with two rows of rolling elements. Easy to replace, but expensive and non-repairable.
- Main symptom of malfunction: A humming or howling noise when driving, which may change when turning.
- Other signs: Vibration on the steering wheel, hub heating, wheel play, extraneous noises (crunching).
- Replacement: Requires strict adherence to instructions and the use of a torque wrench for proper tightening.
- Service life: HUB bearings are maintenance-free, while classic bearings require periodic inspection and lubrication.
- Manufacturers: Market leaders include SKF, Koyo, SNR, NSK, and FAG.
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