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Steps to Check a Hub Bearing Unit
It can be a challenging task to properly diagnose a damaged hub unit bearing. The information below will help you recognize the common causes of noise generation and explain how to examine a hub unit bearing.
Step 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 thread 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. 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 unit bearings.
Step 2: Prior to checking a hub unit bearing, make sure you have the proper tools.
Step 3: Perform a hand rotation check on the wheel. Next, grasp the wheel at the 3 o’clock and 9 o’clock positions. Apply a pushing and pulling force alternately, while oscillating the wheel. Perform a second check, following the same procedure, grasping the wheel at 12 and 6 o’clock positions. In addition, listen and feel for roughness. After making all preliminary inspections, check the hub unit bearing more precisely.
Step 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 caliper is properly supported with either an "S" hook or a piece of wire.
Step 5: Remove the caliper mounting bracket and then remove the brake rotor.
Step 6: Rotate the hub unit bearing by hand. Bearings normally do not loosen up under typical use. If the hub unit bearing 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.
Step 7: To check a hub unit bearing'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.
Step 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 unit bearing as possible. This will provide the most accurate results.
Step 9: Grasp the wheel flange at the 3 o'clock and 9 o'clock positions, and push while oscillating the hub unit bearing approximately 90 degree side-to-side at least five times. Set the dial indicator to zero. Next, pull while oscillating the hub unit bearing approximately 90 degree side-to-side at least five times. Proper loading and oscillation is necessary in order to fully seat the bearings.
Step 10: Observe the total indicator movement. If it exceeds 0.004", replace the hub unit bearing.
Failure to observe the following warnings could create a risk of serious injury!
1) Proper maintenance and handling procedures are critical.
2) Always follow installation instructions and maintain proper lubrication.
3) Never spin a bearing with compressed air; the rolling elements may be forcefully expelled.
Note: This information is not intended to substitute for the specific recommendations of your equipment suppliers. Every reasonable effort has been made to ensure the accuracy of the information contained in this writing, but no liability is accepted for errors, omissions or for any other reason.
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