Hub bearings may not be the first item you think of when you make a fleet maintenance checklist. There are larger components-engines, tires, safety systems-by their very nature, that require more attention from you.

But this does not mean that the wheel bearings can be covered up, because failures can lead to serious consequences, and some are even so serious that the wheels of the truck fly out while driving.

So with this in mind, these are the eight most common potential wheel bearing problems and how to spot them.

The wheel bearing should be set between 1 and 5/1000 inches (0.001 inches and 0.005 inches), preferably in the middle of these two numbers.

NTN application engineer Divjot Singh explained: "If it is tighter than 1000, then you are very close to the preload." "Imagine the lubricant is squeezed out under the rollers. If there is no lubricating layer, there will be metal in the metal contact. Generate heat, which can cause peeling. 

"The way to judge it is high preload is that you will see wear on the large side of the roller," he continued. "So, the roller is tapered-imagine if you were to take a cross section: the top would be smaller, the bottom would be larger. And wear, if it was more on the bottom of the big side, that's how you judge it The way from high preload settings."

Signs of improper bearing settings come from the noise the driver hears on the road.

After hearing this noise, Singh said what the technician would do is isolate which side or axle of the truck it came from.

"Once they narrow down," he continued, "then they will actually check that side and then take apart the wheel ends... then you will see this actual peeling. But if not You can’t see or judge how much damage has occurred when you actually take out the bearing.”

Singh says this is more common than setting the bearings too tight.

"Usually, over time, the bearing settings will become loose due to wear," he explained. "Moreover, if the initial setting is too loose at the beginning, the more severe the wear, the looser it will eventually become. So, you can imagine that if it is too loose, the system will have a lot of excess play and vibration. This may cause a lot of The problem is not limited to wheel swing, seal leakage, ABS and braking issues. Ultimately, too loose a setting can cause the roller/raceway small ends to peel off, which can lead to failure. If the damage is severe, it may even cause the wheel to fall off."

Singh said that the instructions in each case are similar, but you won't know if the bearing is too tight or too loose until the technician opens it to view it.

Specifically, loose bearings can cause the wheels to fall off when the truck is driving-therefore, the consequences can be serious whether from a road safety perspective or from a fleet liability perspective.

Bearing settings that are too loose or too tight are the most common potential failures, but it is also worth a quick glance at other failures.

Overloading is not common and tends to be specific to certain applications—for example, in the field of garbage trucks. Sometimes you will see the entire raceway peeling off-not to the left or right, so it is not improper setting, but overload.

Misalignment can occur when the bearing is not properly seated. Improperly installed bearings can still work normally, but they will not have a full life span like typical bearings. In other words, Singh said this is not a common problem. However, this is possible.

If the bearing collects a lot of dust before installation, it will stick to the anti-rust material on the bearing, causing contamination.

"At the time of installation, we told the technicians to make sure everything was clean, put the bearings and all parts in the box until you were ready to start work," Singh suggested.

"Contamination can also come from incorrect lubrication," Singh continued. "So if the lubricating oil is not clean, or they did not flush the old lubricating oil properly, it could be because of it."

This is a potential problem that may occur during the installation process. Singh pointed out that this is not common, but it can happen if the technician does not use the correct suppression tools.

Fretting corrosion has a rusty appearance and can occur when the rim rotates or creeps inside the hub—but, Singh points out, this is not common at all.

The answer to avoiding these questions is simple: make sure that the wheel bearings are part of your fleet's regular maintenance plan.

As with all maintenance, how often this happens depends on your application or schedule. For example, trucks in garbage applications often need to replace bearings more frequently than road trucks, because the weight of continuous loading and unloading varies greatly. 

There is no particularly correct interval-but, for example, when checking the brakes, it is also a good time to check the wheel bearings, because the necessary parts have been removed anyway.

This article is sponsored by Bower Heavy Duty Bearings of NTN. For more than 100 years, Bower Heavy Duty Bearings has earned a reputation for reliability and performance in the serious world of large drilling rigs and other hard-working vehicles. Learn more about Bower on PowerofBower.com.

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Author: Bower Heavy Duty Bearings by NTN September 7, 2021

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