Auto Service World
Feature   March 1, 2013   by Chris Talbot

Keeping hub assemblies in tip-top shape

Diagnosing hub assembly wear and failure can trip anyone up. The sounds associated with wheel hub and bearing wear and tear can sound suspiciously like other problems related to the tire or even the constant-velocity (CV) joints. However, there...

Diagnosing hub assembly wear and failure can trip anyone up. The sounds associated with wheel hub and bearing wear and tear can sound suspiciously like other problems related to the tire or even the constant-velocity (CV) joints. However, there are some audio and handling cues that can make it easier for the service technician to quickly and accurately diagnose the problem.

Early signs of wear on the wheel bearings will usually be related to noise — typically a growling, humming, squeaking or even a gentle “shushing” sound. There’s a good chance drivers will ignore the persistent sound at first, but as the bearing continues to wear, the sounds get louder and more distracting.

“The worse the problem is, the easier it is to find. When they wear, they’ll usually develop some play in them. You can put the car on the hoist and wiggle and find play in places where there’s not supposed to be play,” said Dwayne Venema, owner of RDV Mechanical in Fort Smith, Northwest Territories.

Venema noted it can be easy to get fooled, and many service technicians have replaced the hub assembly on the wrong side of the vehicle, believing incorrectly they had pinpointed the problem. Today, many shops are outfitted with a Chassis Ear, an electronic device with audio transmitters that can be tie-strapped to the suspension. Each transmitter runs on a different channel, and after a quick drive, it becomes obvious which hub assembly has taken a beating. Venema said it’s a tool he wouldn’t be without, as it saves him plenty of time and makes him more accurate and efficient in diagnosing hub assembly problems.

Another key sign that a hub assembly is failing is a feeling of misalignment while cornering, said Dean Weber, vice-president of sales and marketing at Proforce Automotive in Toronto. Weber said it can feel like the wheel is misaligned or there’s a “jerky” feeling in the steering. Other signs of pending failure include abnormal or uneven tire wear, and if the ABS light is displayed.

“The tech can diagnose this by jacking up the car and wiggle each wheel with your hands. If the wheel gives too much, the bearings may be loose or need replacement,” Weber said.

From inside the car, it can be difficult to determine the problem, said Rick Domin, senior product analyst at The Timken Company.

“The problem is when you’re inside the vehicle and you hear one of these noises, it is sometimes difficult to identify which side it’s coming from,” Domin explained. “It tends to resonate through the car instead of being obvious. That’s where there’s some checking you can do — getting the wheel off, checking the hub assembly for hand play, which is in-and-out movement, looking for grease being expelled from the hub assembly itself, whether it’s up near the CV joint or in between where the rotor and the hub flange would be. If you see excessive amounts of grease, that’s an indication that something is wrong. And then the in-and-out play, the clearance in the hub assembly, generally if it’s over four-thousandths of an inch, you want to replace the hub assembly.”

Since the automotive industry made the switch to front-wheel drive two decades ago, hub and bearing assemblies have essentially become mostly unserviceable. Aside from automotive models at least 20 years old (or 10 years in the case of light trucks), there is rarely a need to disassemble the wheel bearing, clean out the assembly, repack it with grease and then reinstall. That’s still common in commercial vehicles, but for automotive technicians, it may only be necessary to do a repack a few times per year — specifically when working on older model vehicles.

Asking customers pointed questions to unveil these problems will save service technicians time in finding the problem.

Although there’s no average lifespan for a wheel hub assembly, road conditions and extreme temperatures can certainly shorten its lifespan. Heat is an assembly’s biggest enemy because it can deteriorate the seal faster, allowing for contamination of the internal lubricant, said Domin. Extreme temperatures will wear out the seals, but that can be accelerated by bad wheel callipers or brake failure. Moisture in the assembly will also cause unnecessary wear.

Road conditions can also have a serious impact on an assembly’s life. Rough rural roads, abrasives such as sand and salt on roadways, and impact damage from potholes and collisions will also contribute to the wear and eventual failure of a hub assembly, said Matt Bischof, product manager for FAG hubs and wheels at The Schaeffler Group.

Once the diagnostic has been completed and the problematic hub assembly identified, removing and replacing the part isn’t difficult, but Bischof warned to ensure the proper torque is used when bolting on the new assembly. Provided the manufacturer’s torque specifications are used in putting the bolts back in, the service technician won’t cause damage.

“There are some things when you’re changing them that you have to do. The most important is the proper torque of the axle part,” Timken’s Domin said. “That will ensure the longest life. Inadequate or improper torque is the number one cause of installation error. Another part of the hub that may not seem as critical but is, is actually the real stud torque. That won’t necessarily affect the bearings themselves as much as brake pedal pulsation, rotor run-out and abnormal brake failure.”

While hub and bearing assemblies are replacement parts, that doesn’t mean inspecting the assemblies can’t be slotted into a regular vehcile maintenance check. In fact, it is quite the opposite.

“It’s basically down to checking them periodically or if there’s a complaint of noise by a customer, that would be cause to check it,” said Schaeffler’s Bischof.

According to Domin, every little bit counts when ensuring a long life for a hub and bearing assembly.

“Good rubber and the only reason I say that is tire imbalance issues or misalignment issues, meaning a good front end. Ball joints, tie rod ends and good rubber on the road will definitely help improve the life, where those issues could decrease the life if they’re allowed to come out of adjustment,” Domin said. “But as far as an individual wanting to maintain their hub assembly, the beauty of these is that they are self-contained, they’re pre-greased, pre-sealed and pre-set from the factory. That means they’re easy to install and there’s no maintenance. But that’s also the downfall, that there’s no maintenance. You can’t clean them up, check them over and put them back together.”

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