Everything You Ever Wanted to Know About Wheel Bearings

Why are wheel bearings for Huntersville vehicles important? It's simple: your wheel bearings keep the wheels on your vehicle. In today's Tuffy Tire & Auto Huntersville post, we'll discuss more about wheel bearings and how you can make sure they can do their very job while you drive around Huntersville, North Carolina.

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Wheel bearings are pretty simple parts. They're made of high quality steel and are engineered to last 100,000 miles (160,000)  or more if properly cared for. The bearings do two jobs: First, they allow the wheel to freely rotate with as little friction as possible. Second, they support the weight of the vehicle. For example, if your car weighs 3,600 pounds ( kilogram), each wheel has to support approximately 900 pounds (400 kilograms). That's a lot of heavy lifting over those long distances.

Even though wheel bearings are pretty straightforward, they need to be in near perfect condition to do their job for Huntersville vehicles. The bearings are packed with heavy grease to lubricate and protect them. A seal keeps the grease in and water and dirt out. It's when the seal starts to leak that problems begin. The grease can become contaminated, causing the wheel bearings to overheat and ultimately fail.

The first sign that your wheel bearings are in trouble is an unusual noise coming from a wheel. It could be a chirping, growling, rumbling or a cyclic sound. The noise could get louder or even disappear at certain speeds. Your technician at Tuffy Tire & Auto Huntersville can inspect for bearing wear by lifting the vehicle and checking for play in the wheel.

Now some wheel bearing assemblies are factory sealed. That means that they cannot be serviced – they can only be replaced. Those that aren't sealed can be serviced on schedule at Tuffy Tire & Auto Huntersville. The bearings are removed, cleaned and inspected. If the bearings are still good, they're re-installed – if not, they're replaced. They are then packed in grease and a new seal is installed.

If your vehicle has a factory sealed wheel bearing assembly, the entire assembly needs to be replaced when trouble arises. Unfortunately, the parts are pretty costly – but they usually last about 150,000 miles (240,000 kilometers) as long as the seals hold up.

Now, even a good seal cannot keep out water that's exerting pressure on the seal. So if you've driven through hub-deep water, your bearings should be cleaned and repacked if they're serviceable. If you have factory sealed bearings, you just need to watch for signs of premature failure. If your wheel bearings can be serviced, your manufacturer's owner's manual will recommend an interval, usually around 30,000 miles (50,000 kilometers).

If you have any sort of trailer, don't forget its wheel bearings. They probably need to be serviced even more frequently. This is especially true for boat trailers that are used to launch the boat by backing it into the water. These should be serviced every year, usually at the end of the season so that the bearings don't have the opportunity to rust all winter.

So what happens to Huntersville vehicles if wheel bearings fail? Well, the wheel can literally fall off the vehicle. I don't need to tell you how that could be. So check with your service advisor at Tuffy Tire & Auto Huntersville and see if your vehicle's wheel bearings can be serviced and when it's recommended. Listen for warning signs. If you've been fording streams or puddle surfing after rainstorms, be especially vigilant.

Visit the automotive professionals at Tuffy Tire & Auto Huntersville for a wheel bearing inspection. 

Wheel bearings play an important role in the ride satisfaction of your customers’ vehicles. To prevent comebacks by performing the service right the first time, check out the following wheel bearing Q&A:

How much load can a wheel bearing carry?

On a typical passenger vehicle weighing around 3,400 pounds, each pair of front-wheel bearings, as well as the rear-wheel or axle bearings, support around 850 pounds, depending on the weight balance and driveline configuration. If it’s a 6,000-pound SUV, each bearing might carry about 1,500 pounds. This load is concentrated on the relatively small bearing surfaces.

These loads do not even take into account the dynamic loads produced by cornering. These loads put on the bearing are called thrust and radial loads, and are the forces the bearing must endure when the vehicle is cornering or braking. Another force that cannot be measured is the force of impacts from potholes and curbs.

Besides reducing friction, what else does wheel bearing grease/lube do?

Lubricants aid in carrying away heat and protecting bearing surfaces from corrosion, as well as reducing friction.

How long do wheel bearings last?

Most serviceable wheel bearings need maintenance every 25,000 to 30,000 miles, or during every brake service.
The average life of a sealed wheel bearing and hub assembly is about 85,000 to 100,000 miles, without the opportunity for a technician to repack the bearings. You may only have one chance during a vehicle’s life to replace these parts. If you miss this opportunity, it may be gone forever.

When are bearings replaced?

According to a recent Babcox Research survey, 51% of bad wheel bearings are identified and replaced as a result of a customer complaining about noise; 24% are found during a brake job; and 19% are discovered during an alignment.

What is the leading cause of wheel bearing failure?

The leading cause of a wheel bearing failing is its seal. The inside of a bearing can be a hot place. When a bearing is cooling off, the contracting metal, air and lubricant can create a vacuum that is hopefully held by the seals. If the seals are worn and can’t hold the vacuum, the bearing or sealed hub unit will suck in outside air, debris and water. In some parts of the country that use salt on the roads, it is almost as bad as ocean water on wheel bearings.

As these contaminants circulate through the grease and between the races and bearings, the components wear. Once a bearing is worn, the wear rate is accelerated by seals that can no longer keep out contaminants, and increased heat may break down and eventually expel the lubricants. This is a slippery slope that could quickly lead to catastrophic failure.

Can too much grease cause a wheel bearing to fail?

Over-filling a bearing with too much grease can cause excess churning of the grease during operation and high temperatures, resulting in overheating and excess grease purging (leaking). Overheating occurs because the heat generated cannot dissipate correctly, continually building until damage occurs.

When a bearing overheats and pushes out the grease, the sealing lip can be damaged and “blown out” in the reverse direction.

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Do I need to uncover why the previous bearing failed?

Yes. When a bearing wears out, it is usually a case of inadequate lubrication, faulty installation or improper adjustment. For the repair to be successful, you must first determine why the previous bearing failed. For sealed hub units, examining the internal bearings and races is impossible.

Interview the customer to find out what kind of roads they drive on and what types of loads they carry. If the customer overloads the vehicle, bearing damage could be inevitable. The most common failure pattern for bearings is for those on the passenger side of the vehicle to fail first. The passenger side bearings are exposed to the most standing water in the gutter. If the bearings on the driver side of the vehicle fail first, take an ext-remely close look at the passenger side bearings, as failure may not be far behind.

The lubricant and bearing surfaces have a dark appearance and coating. What happened?

Burned or oxidized lubricant may leave a dark coating on bearing surfaces. If a bearing overheats, the hot lubricant breaks down and can cause scoring and even etching of the bearing surfaces. Also, water and other corrosive elements can create this condition, which leads to spalling down the road. Remember that with tapered roller bearings, excessive pre-load can mimic this same damage. If a bearing gets really hot, cages and seals could be deformed and lead to bearing lockup.

Can wheel bearing grease wear out?

Grease is a precise combination of oil, thickener and additives. It acts like a sponge to retain and release the oil. As a result of time and temperature conditions, the oil release properties can become depleted. When this occurs, the grease is worn-out.

A cheaper hub unit has the same appearance as a high-quality, brand-name unit. What is the difference?

Bearings are precision products that require complex manufacturing processes. Inferior bearings that use low-quality steel and have poor heat-treating can wear and spall prematurely. In addition, the poor-quality steel may have inclusions of hard or soft metal that can cause a premature failure.
In summary, an inexpensive bearing may look the same as a high-quality bearing, but it is what you can’t see that makes a difference between a comeback and a satisfied customer.
Also, some cheaper hub units are using smaller bearing sizes than the OEM intended. This can lead to premature failure. Unfortunately, the only way to tell is to destroy the new bearing.

Why can’t a technician use an impact wrench to secure the axle nut?

While it may appear easier to use an impact wrench, it is not recommended. OEM and bearing manufacturers always recommend using a torque wrench for installation. During removal, an impact wrench can damage the axle nut threads and shock the CV joints. It also can create a false sense of security when adjusting a nut or bolt, which then may be under- or over-torqued. This can leave a hub assembly susceptible to failure.
Also, in almost all cases, use a new axle nut. Some axle nuts are designed to be used only once, and cannot be adjusted.

What is the right way to adjust a tapered roller bearing?

Always check the service information for the correct procedure. Overtightening adjustable tapered roller bearings is a common error that can lead to premature failure. Tapered roller bearings on the front of RWD vehicles are never preloaded. They’re snugged up with no more than 15 to 20 ft.-lbs. of torque while rotating the wheel to make sure the bearings are seated. Then the adjustment nut is loosened 1/6 to 1/4 of a turn, and locked in place with a new cotter pin. As a rule, endplay should be about 0.001 to 0.005 inches.

How does a technician know when to replace and repack wheel bearing grease?

Colored and UV dyes can be added to a grease as assembly aids or to facilitate inspections. The original color of a grease has little to do with its performance.

Automotive wheel bearing grease contains corrosion inhibitors, plus anti-wear and water-resistant additives, offering superior protection in challenging environments.

A softened sealing lip surface is the sign of a compatibility problem with the grease and seal.

The wrong grease can cause a rubber seal to swell and disintegrate. Fresh grease is smooth and buttery compared to water-laden grease, which is milky white in appearance. As little as 1% water in grease can have a significant impact on bearing life.

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