Auto Service World
Feature   November 1, 2005   by Auto Service World

Counter Talk: Knowledge Building: Hub Bearing Assemblies

Over the past number of years, automotive applications have gone almost entirely to hub bearing assemblies.

It can be a challenging task to properly diagnose a damaged hub bearing assembly. This information will help you and your customers to recognize common causes of noise generation and know how to examine a hub bearing assembly.

This information, while directed at the technician in particular, can help a counterperson understand the procedure required for determining if there is a problem, and can serve as a reminder that you can pass along to your customers.

1) The first step is to verify the source of any unfamiliar noise.

Often this can be attributed to road surface conditions such as newly paved roads or roads with uneven surface characteristics, which can cause unusual and intensified noises. The tread design, composition and wear patterns of vehicle tires can be another source of unfamiliar noise. Unusual wear patterns are generally caused by lack of tire rotation, poor alignment, improper pressure or worn suspension parts. In some cases, tread-block feathering due to hard driving, as a result of a “track day” for instance, can generate significant noise.

After eliminating noise generation caused by road surface conditions, tire design and wear patterns, it’s time to make a more detailed examination of the wheel assemblies as well as the hub bearing assemblies.

2) Prior to checking a hub bearing assembly, make sure you have the proper tools.

3) Perform a hand rotation check on the wheel. Next, grasp the wheel at the 3 o’clock and 9 o’clock positions. Push while oscillating and also pull while oscillating the wheel. Perform a second check, following this same procedure, grasping the wheel at the 12 and 6 o’clock positions. In addition, listen and feel for roughness. After making all preliminary inspections, check the hub bearing assembly more precisely.

4) If applicable, remove the wheel cover to access the lug nuts. Remove the lug nuts and the wheel and tire assembly. Next, remove the caliper from the caliper mounting bracket. To prevent damage to the brake line due to the weight of the caliper, make sure the caliber is properly supported with either an “S” hook or a piece of wire.

5) Remove the caliper mounting bracket and then remove the brake rotor.

6) Rotate the hub bearing assembly by hand. Bearings normally do not loosen up under typical use. If the hub bearing assembly appears to be loose, the bearing may be damaged, the axle nut may have backed off, or the axle nut may not have been properly clamped. Any roughness, looseness or noise from the bearing is an indication that the bearing is damaged and needs to be replaced.

7) To check a hub bearing assembly’s internal clearance, a dial indicator with a magnetic base is required. To obtain accurate readings from the dial indicator it is important to thoroughly clean and smooth the surfaces where the dial indicator base and tip will be placed. Carefully use a fine file, wire brush, emery cloth or honing stone as appropriate to remove any debris, nicks or burrs.

8) The dial indicator base should be placed rigidly on the knuckle or a secure portion of the suspension. When setting the dial indicator tip, the indicator itself should have ample travel for the variation around the face. Position the indicator tip perpendicular on the wheel pilot as close to the center of the hub bearing assembly as possible. This will provide the most accurate results.

9) Grasp the wheel flange at the 3 o’clock and 9 o’clock positions, and push while oscillating the hub bearing assembly approximately 90 degrees side-to-side at least five times. Set the dial indicator to zero. Next, pull while oscillating the hub bearing assembly approximately 90 degrees side-to-side at least five times. Proper loading and oscillation is necessary in order to fully seat the bearings.

10) Observe the total indicator movement. If it exceeds 0.004″, replace the hub bearing assembly.

Special thanks to Timken for information used here. Images courtesy Schaeffler Canada Inc. Automotive-Aftermarket Division, makers of FAG bearings.

Frequently Asked Questions

Hub bearing assemblies have become almost universal in new automotive applications. As the technology has evolved, they have incorporated more and more features, such as integrated ABS sensors.

These new generation wheel bearings are certainly more expensive than the separate bearing assemblies that they replace, but there are a number of important reasons for the transition.

Why are more vehicles using hub assemblies today?

Hub assemblies are unitized, maintenance free and non-serviceable units that are pre-set, pre-greased and pre-sealed, making installation easier and increasing product reliability for enhanced performance. These hubs require no maintenance or handling, which eliminates the need for preventative maintenance, grease and/or future adjustments.

Are all aftermarket hub assemblies created equal?

Perhaps not. Care should be taken to ensure that hub assemblies meet or exceed original equipment specifications. To meet these standards, a hub assembly must not only meet the dimensional measurement requirements for original equipment specifications, but they must also match the material and performance standards.

Can an impact wrench be used to remove or install a hub assembly?

While it may appear to be easier to use an impact wrench, it is not recommended. Instead use a certified, calibrated torque wrench. Impact wrenches can damage the axle nut, threads and components. It can also create a false sense of security when adjusting a nut or bolt, which may be under- or overtorqued.

This can leave a hub assembly susceptible to failure.

Do you need to torque the axle nut or the lug nut?

Yes. It is imperative that the manufacturer’s specifications and instruction manual be followed to assure the hub is installed correctly. Failure to follow the manufacturer’s installation instructions and follow the proper installation procedures can cause equipment failure, creating a risk of serious bodily harm.

Can you replace the bearings or seals in a hub assembly?

No, because the hub assemblies are unitized, maintenance free and non-serviceable. Most hub assemblies are designed with a unitized bearing or flange that is intricate to the hub and/or bearing housing, which are not replaceable.

Do wheel studs come with all hub assemblies?

No. While most hub assemblies do include the wheel studs, there are some that do not. Reusing old studs with a new hub is not recommended.

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