AfterMarketNews AfterMarketNews Auto Care Pro AutoCareCareerHub Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service Speedville

Thorough Brake Inspections Are Comeback Preventers And Profit Builders

How many times have you seen a hand-painted sign in a shop window that advertised a menu-priced brake pad replacement for “$XX.95 per axle.” Of course, a menu-priced brake replacement would be good if a simple brake pad replacement would cure all...

Read more...

Automotive Pet Peeves 2: Reader Feedback Is Overwhelming

How many auto repair pet peeves are out there? Well, enough of them that one article wouldn’t hold them all. I’ve received so many emails, texts and phone calls about my article in the February issue that I thought: why not put everyone’s pet peeve...

Read more...

Air Filter Show & Tell: Seeing Is Believing

Air filters are normal wear items that ­require regular checks and ­replacement. Their role is to trap dirt particles that can cause damage to engine cylinders, walls, pistons and piston rings. In fuel-injected vehicles, the air filter also plays...

Read more...

ZF 8-Speed Transmission Replacement

The ZF 8HP transmission made its debut in 2009, and since its introduction, has been one of the top choices for international car manufacturers. BMW, one of ZF’s largest customers, uses the 8HP across its entire product portfolio. BMWs featuring...

Read more...

Shop Folds After Shoddy Brake Work Endangers Woman

A Florida woman was thankful to walk away without injury after her vehicle’s brakes went out for the second time in as many months due to negligence on the part of her local repair shop, ABC Action News reported. Shelly Darling of Zephyr Hills, FL,...

Read more...

Air Ride Diagnostics: Reservoirs and Compressors

Just about every Asian and European luxury import nameplate manufacturer has a 7- to 10-year-old vehicle on the road with an air-ride suspension at all four corners. Chances are one of these vehicles will be coming to your shop sooner rather than later. Regardless...

Read more...

Can Cordless Power Tools Replace Pneumatic Tools?

I recently attended Milwaukee Tool’s annual media tool preview event where they unveiled over 80 new products that will be available later this year and early next year. Milwaukee Tool is known primarily as a leading supplier of professional-grade power...

Read more...

OTC's Technician Challenge Tour Will Award Ultimate Diagnostics for Life

The OTC Technician Challenge is going on tour with dates in six states, showcasing the Encore with new Bravo 2.0 software. Technicians nationwide will compete to win one of three Ultimate Diagnostics for Life packages. Ultimate Diagnostics for Life winners...

Read more...

New Productivity Features Added To Coverage In Snap-on Software Upgrade 15.2

Snap-on has increased its vehicle coverage in the new Software Upgrade 15.2 for the Auto-ID, One-Touch Full Vehicle Code Scan and the One-Touch Code Clear features to provide effective, accurate and fast diagnostics out of the box and miles down the road. The...

Read more...

BMW Recognized for Engine-Building Excellence

BMW Group’s engine-building prowess was recognized with four wins at the latest International Engine of the Year Awards. The drive unit in the BMW i8 earned two class wins as well as being declared overall winner, with a further class win being garnered...

Read more...

Diagnostic Dilemma: The Case of the Missing Code

When doing mobile diagnostic work, no-code stalling complaints are a major part of your agenda. In most cases, the client shop is simply too busy to duplicate the failure or, in some cases, a long test drive will yield nothing in the way of useful...

Read more...

Secondary Ignition: The Art of Spark

What is a coil? From the beginning of the internal combustion engine, several different ignition systems have been used to create a high-energy spark. The most popular system, and the one that’s in use today, is a step-up coil. A coil is nothing...

Read more...

Home Brakes Bearings Wheel Bearing Failure Diagnostics

Print Print Email Email

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 saround 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 that are put on the bearing are called thrust and radial loads. These are the forces the bearing must endure when the vehicle is cornering or braking. Another force that can not be measured is the force of impacts from potholes and curbs.

Most serviceable wheel bearings need maintenance every 25,000 to 30,000 miles, or during every brake service. But, the average life of a sealed wheel bearing and hub assembly is about 85,000 to 100,000 miles, without the opportunity for you 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.

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

Why Bearings Fail
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 and possibly change their metallurgy.

A driver may notice noise coming from the vicinity of the wheel, maybe some steering wander or looseness in the steering, and abnormal tread wear on the front tires. The noise may change when turning, or become louder or even disappear at certain speeds. This noise should not be confused with the clicks and pops produced by a worn outer CV joint on a FWD car. A bad outer CV joint usually only makes noise when turning, not when driving straight ahead.

Once a bearing is worn, the wear rate is accelerated by seals that no longer keep out contaminants, and increased heat may breakdown and eventually expel the lubricants. This is a slippery slope that could quickly lead to catastrophic failure.

Looking Closer
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. Also, ask 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 extremely close look at the passenger side bearings, failure may not be far behind.

Metallurgy
Most bearing components are heat-treated to harden the metal. But, the heat-treating can only penetrate so far into the metal. Once the bearing has worn through this layer, rapid and catastrophic wear occurs to the softer metal below. This type of fatigue failure is called “spalling.” This kind of damage causes the metal to come off in flakes. 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. Burned or oxidized lubricant may leave a dark coating on bearing surfaces. 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 leading to bearing lock-up.

Seals are critical components for the longevity of a bearing. If contaminants from the outside find their way inside, this could cause a wear pattern called bruising. Never re-use seals. Used seals can leak and contaminate brake linings or cause premature bearing failure.

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. Also, 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.

Installation
Installing wheel bearings is a relatively straightforward job. But, there are several key items to remember when dealing with serviceable or sealed hub units.

On serviceable bearings, the most important service tip is to invest in a good set of seal drivers. Even a slight distortion in a seal made during installation can shorten the life of the bearing inside. Also, do not skimp on the quality of the grease. Many parts suppliers carry wheel bearing-specific grease that can do an excellent job of protecting the bearings.

Unit hub assemblies combine bearings, seals, hub and spindle in one pre-assembled unit that simply bolts to the suspension. These are “maintenance free” and non-serviceable units that are pre-set, pre-greased and pre-sealed. Some units may require you to install wheel studs. If at all possible, install new wheel studs.

While it may appear to be 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 can also create a false sense of security when adjusting a nut or bolt, which 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 can not be adjusted.

Load paths for in a tapered roller bearing.

Adjusting
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 turn, and locked in place with a new cotter pin. As a rule, endplay should be about 0.001 to 0.005 inches.

There should be no play on most FWD cars, but up to 0.010 inch of play in the front bearings may be acceptable on RWD cars and trucks with adjustable bearings. On FWD cars with adjustable tapered roller rear wheel bearings, the bearing adjustment procedure is usually the same as with RWD vehicles (zero pre-load), but some do require a slight pre-load.

The following two tabs change content below.

Andrew Markel

Andrew Markel is an ASE Certified Technician and former service writer, and he brings this practical knowledge to the Brake & Front End team as editor.

Latest posts by Andrew Markel (see all)

Latest articles from our other sites:

ZF 8-Speed Transmission Replacement

The ZF 8HP transmission made its debut in 2009, and since its introduction, has been one of the top choices for international car manufacturers. BMW, one of ZF’s largest customers, uses the 8HP across...More

ACDelco Unveils Training Recognition Program For Technicians

ACDelco is rewarding technicians and aftermarket service centers for making the commitment to enhance their skills through ACDelco training. The ACDelco Technician Training Recognition Program awards technicians...More

ZF 8-Speed Transmission Replacement

The ZF 8HP transmission made its debut in 2009, and since its introduction, has been one of the top choices for international car manufacturers. BMW, one of ZF’s largest customers, uses the 8HP across...More

Shop Folds After Shoddy Brake Work Endangers Woman

A Florida woman was thankful to walk away without injury after her vehicle’s brakes went out for the second time in as many months due to negligence on the part of her local repair shop, ABC Action News...More

Homak Has Serious Tool Storage Covered

Homak has introduced its new 35" seven-drawer Service Cart. It has plenty of storage for all your tools and is offered in three unique, high-gloss finishes. Featuring full-extension gas struts in...More

Alert Stamping Introduces Versatile Rechargeable Hood Light

Alert Stamping’s new rechargeable SMD LED Hood Light offers dual brightness levels: 1,200 lumens on high and 700 lumens on low. Its bracket extends up to 88" and can stand on flat surfaces. The bottoms...More

Chicago Auto Show Display Takes 1.0L EcoBoost Apart

One of many highlights in the Ford booth at the 107th Chicago Auto Show was a large layout of the pieces that make up the first-ever Ford three-cylinder EcoBoost engine. This 1.0 liter turbocharged, direct-injection...More

Performance V6 and Four Bangers

Any engine builder worth his or her torque wrench keeps their eyes open. They’re looking for anything and everything to make work easier, better and, of course, more profitable. And just as important...More