The 8 Most Common Wheel Bearing Maintenance Issues

Wheel bearings may not be the first item you think of when making your fleet's maintenance checklist. There are bigger components—the engine, the tires, the safety system—that, just by their nature, demand more of your attention.

 

But that does not mean that wheel bearings can be swept under the rug, as failures can lead to serious consequences, some even as severe as the truck's wheel flying off while driving.

 

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

 

1. Bearing set too tight

 

Wheel bearings should be set between 1 and 5/1000s of an inch (0.001-in. to 0.005-in.), and ideally in the middle of those two numbers.

 

If it's tighter than one thousand, you're running very close to preload. Imagine the lubrication getting squished out below the rollers. If there's no lubrication layer, there will be metal on metal contact creating heat, which leads to flaking.

 

The way to tell that it's a high preload is that you will see wear on the large side of the roller. So, the rollers are tapered—imagine if you were to take a cross section: The top would be smaller, and the bottom would be larger. And the wear, if it's more on the bottom on the large side, that's how you can tell that it's from a high preload setting.

 

The indication of an improperly set bearing comes from a noise the driver will hear on the road.

 

After hearing this noise,  technicians will isolate which side of the truck, or which axle, it's coming from.

 

Once they narrow that down, then they will actually inspect that side and then take the wheel end apart.. That's when you will see this actual flaking. But, without actually taking the bearing out, you cannot see or you cannot tell how much damage has already happened.

 

2. Bearing set too loose

 

This, Singh says, is more common than the bearing being set too tight.

 

Typically what happens is, over time, bearing setting will become loose because there's wear and tear," he explains. "And, if the initial setting was too loose to begin with, the more wear and tear happens, the looser it is going to get eventually. So, as you can imagine, if it's too loose, there's going to be a lot of excess play and vibration in the system. This could lead to a multitude of issues not limited to wheel wobble, seal leakage, ABS and braking problems. Eventually a too loose setting will cause flaking at the small end of the rollers/races leading to failure.  If damage is severe, it could even lead to the wheel coming off.

 

The indications are similar in each case, but you won't know whether the bearing is too tight or too loose until the technician opens it up to have a look.

 

A loose bearing, specifically, is what can lead to the wheel coming off while the truck is being driven—thus, the consequences can be severe both from a road safety perspective and also from a fleet liability perspective.

 

The bearing being set too loose or too tight are the most common potential failures, but it's worth quickly running through the others as well.

 

3. Bearing overload

Overloading isn't common and tends to be specific to certain applications—in the garbage truck segment, for instance. Sometimes you'll see flaking across the entire raceway—it's not towards the left or to the right, so it's not from an improper setting, but from overloading.

4. Misalignment

Misalignment occurs when the bearings are not seated properly. Improperly seated bearings will still function, but they will not have the full life of a typical bearing. That said, Singh says that this is not a common issue; however, it is possible.

 

5. Contamination

If the bearing has collected a significant amount of dust before installation, it can stick to the rust preventative substance on the bearing and this could lead to contamination.

 

While installing, we tell the techs to make sure everything is clean, keep the bearings and all the parts in the boxes until you're ready to work on it.

 

6. Improper Lubrication

Contamination could also come from faulty lubrication. So, if the lubrication is not clean or if they did not properly flush the old one out, it could be from that, too.

 

7. Impact Loads

This is a potential issue that can happen during installation. It's not very common, as Singh notes, but possible if technicians do not use the proper pressing tools.

 

8. Fretting Damage

Fretting corrosion has a rusty appearance and can occur when the race spins or creeps inside of the hub—but, Singh notes, this is not very common at all.

 

Maintenance Frequency

The answer to avoiding these issues is a simple one: Make sure wheel bearings are part of your fleet's regular maintenance schedule.

 

How frequently that happens, like all maintenance, depends on your application or schedule. Trucks in the refuse applications, for example, tend to need more frequent bearing replacements than their over-the-road counterparts, because of the wide variations in weights from the constant loading and unloading.

 

There's no specifically correct interval—but, for instance, when the brakes are being checked makes for a good time to check the wheel bearings as well since the necessary components are being removed anyway.

 

Qianyu Auto Parts Co., Ltd. is a professional truck bearing manufacturer with more than 20 years of experience in truck bearing manufacturing. The products have passed ISO/TS16949, ISO9001, EU CE certification and other certificates, and the quality is reliable. Approved by customers in more than 50 countries. If you are interested in our products, please contact us now!

Why Wheel Bearings Are Important, And What Happens When They Fail

Wheel bearings are designed to promote efficient wheel rotation but can equally become annoying on a long drive when they decide to fail. So here is what can go wrong and how to go about fixing them.

 

Wheel bearings play an important role within the drivetrain of any vehicle, as they provide the first connection between the moving and static areas of the car. A bearing - in its simplest form - is a friction reduction device placed within something like a wheel to aid efficiency of rotation. This is achieved as rolling produces much less friction force than sliding.

 

A car's wheel bearing does this by using small metal balls that roll between two smooth rings of metal. Along with grease, the bearing rotates in-tandem with the wheel's rotation, the rolling motion of the balls allowing the wheel hub to rotate as freely as possible.

The wheel bearing is housed within the hub assembly, providing the static connection with the hub carrier through an outer ring or 'racer'. The driveshaft travels from the transmission and passes through the centre of the wheel bearing through the inner ring, creating the rotational partnership. Roller bearings are used generally on the driven wheels of a vehicle, while tapered bearings are predominantly used on the non-driven wheels.

 

Like all mechanical parts on a car that rotate, rub and roll, they tend to wear out. And the tell-tale sign of a wheel bearing that's had its day is a constant drone or hum from whichever wheel is affected at various speeds. There are three general causes of a dodgy bearing:

 

ㆍIncorrect alignment due to poor installation

ㆍA damaged or leaking bearing seal

ㆍAn inward collision due to a side impact

 

The most common mechanical failure is due to a seal leak, which allows the lubricating grease to exit the bearing, and water and grit managing to worm its way in. This all amounts to the degradation of the balls and the outer and inner housing of the bearing, often creating that gritty, skimming sound as the wheel is rotating. Looking inside a worn-out bearing, there will often be small specs of metal that have broken off from inside the bearing itself and are grinding their way around the racers, causing more damage.

 

Considering wheel bearings are generally made from hardened steel, they can stand a serious amount of rotational abuse. But apply heat (through lack of lubrication) and water (broken seal) and all hell can break loose.

To replace a wheel bearing properly, it has to be popped out of the hub assembly, preferably using a hydraulic press. Problems can arise with the re-installation of the new bearing, as the alignment must be accurate to avoid the bearing wearing out rapidly and causing further pain. Wheel bearings should last tens of thousands of miles, but many mechanics will simply hammer the bearing back into the hub assembly instead of precisely aligning it and using the aforementioned press. This will inevitably lead to the bearing not rotating in the perpendicular fashion that it was designed for, accelerating wear and damage to the part.

 

Most online parts stores will now sell the entire hub assembly with the wheel bearing pressed into it, saving the hassle and potential scope for mistakes within the specific bearing assembly.

 

If left to wear down further, a wheel bearing could seize and lock the axle, so think carefully about your timing if the classic wheel bearing drone starts. However, considering the forces that a drivetrain has to counteract during its lifetime of usage, it is impressive how long wheel bearings can last if inserted properly and looked after.

 

Although it can be a labour-intensive job if one was to fail, the shift to selling entire hub assemblies should make a bad wheel bearing fixable from home, with a decent tool kit and a bit of know-how. So do not fret the next time that horrid whir begins to creep into the cabin, as a fix may be only a ratchet spanner away.

 

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