Today’s wheel bearings, like many other components, have become so dependable that we don’t pay much attention to them until there is a complaint. The typical wheel bearing grumbles are about strange noises, rumbling feelings or an anti-lock brake (ABS), electronic stability control (ESC) or traction control system (TCS) system light or issue.
Often the customer wants the exhaust looked at because the noise they hear gets louder the faster they drive and they translate that to an exhaust noise. Failed wheel bearings cause noises but that’s not the only concern they can cause. Repetitive brake rotor vibration failures, steering issues and strange tire wear can be attributed to a failed or failing wheel bearing assembly.
But wheel bearings are often overlooked during a diagnostic because there aren’t any of the typical wheel bearing noises associated with the complaint. Wheel bearings must deal with several forces and the loads they generate: gravity, acceleration, braking and cornering are some of the forces and they create radial and axial loads. Road grime, brake dust, brake heat, pot holes and a myriad of other conditions are taken into consideration during wheel bearing designs allowing the average wheel bearing to spin about 75 million revolutions by the time it has travelled 100,000 miles. Even the best wheel bearing can eventually fail and when that time occurs, proper replacement procedures for the wheel bearing design used need to be followed, to ensure the same durability as the original equipment one provided.
The taper roller bearing (TRB design)
This older, but faithful style wheel bearing design is used on the non-driven front or rear wheels. The TRB was the most generic form of wheel bearing assembly used until front wheel drive became the norm.
Each TRB cone assembly consists of a tapered inner race, tapered rollers held in place by a cage and the cup or outer race. TRBs don’t have any integrated seals and are more expensive to produce then ball bearings. Used in pairs as an inner and outer cone unit, the TRB is much better at dealing with any small imperfections in alignment or fit and deals with the axial loads placed on the bearing surface better than a deep groove double ball bearing assembly.
The TRB was often just serviced if brake rotors were being replaced, but the TRB does require regular service due to moisture intrusion and grease breakdown. Cleaning and repacking TRBs that aren’t noisy, rough feeling, showing any rust or other issues, can be done by forcing the old grease out with new grease, or a solvent can be used.
When forcing in the new grease, pay attention to the color of the grease coming out to ensure that only the new, fresh grease is surrounding the rollers. And if a solvent is used, care must be taken to remove all traces of solvent before new grease is installed. The proper manufacturer-specific grease is also important, and so is the condition of the hub’s seals. If the TRB assembly has been leaking grease, this is an indication the seals are worn out, not only allowing grease out, but moisture and other contaminates in.
Moisture is the bearing’s enemy: it causes corrosion, and that corrosion leads to debris that accelerates bearing surface wear. Proper bearing preload is also vital to the TRB. The TRB needs to be set first by tightening the spindle nut to the proper torque, then the specific manufacturer’s procedure must be followed carefully before the cotter pin or retaining device is installed. The average TRB-equipped car or pickup was torqued to around 12 ft.-lbs., but some large truck applications can be a much as 400 ft.-lbs.
The Gen 1 wheel bearing design
The Gen 1 is commonly referred to as a cartridge-style wheel bearing or hub bearing. The Gen 1 features a double-row angular contact bearing assembly. The Gen 1 became a preferred bearing choice for small and medium front-wheel-drive wheel applications, but have also been used on some non-driven wheels in an integral bearing/brake drum/hub assembly.
The Gen 1 assembly is composed of a single outer race, two separate inner races, bearing cages and typically ball bearings (tapered bearings can be use in tight space applications). The Gen 1 is also sealed and lubricated for life at the factory. The Gen 1 bearing delivers adequate support to deal with induced axial and radial loads that are transferred through the front wheels, especially when turning. The Gen 1 may also incorporate an impulse/encoder ring, which is integral to the outer seal. This impulse ring provides wheel speed information to the ABS, TCS or ESC systems.
Replacement of a Gen 1 bearing can be challenging and labor intensive. The use of specialized tools to facilitate replacement is a must due to the interference fit nature of this style of bearing into the knuckle assembly. A hydraulic press can be used if the knuckle is removed or a hub tamer tool can be used for on-the-vehicle service. The flange (wheel hub) will have to be removed from the old bearing and care must be taken to make sure that it isn’t damaged or bent in the process. Slide hammers can easily distort or crack the flange, but they can and are used with proper care.
Remember not to use the actual vehicle’s wheel nuts to hold it to the flange, as they can be damaged and subsequently may not seat properly against the wheel.
Flange removal is one area where a hub tamer kit really shines. It will remove the flange safely, easily and with reduced effort. But even when using a hub tamer, press or slide hammer, typically one inner race will remain attached to the flange. This inner race has to be removed without damaging the machined surface underneath it. The use of a puller works, but I have found that a small zip cut and a chisel usually make it split with no damage to the flange or the machined mating surface. Many bearing manufacturers will tell you that it is best to install a new flange as they are often already bent or cracked from hitting curbs and other road-related injuries.
After the flange is removed, the snap ring retainer (if used) will need to be removed, allowing the bearing to be pressed or pulled from the knuckle. Next, the knuckle and flange need to be cleaned and inspected, paying attention to the retainer ring groove and the seating area before any reassembly starts, as trapped debris can result in premature bearing failure.
It is also imperative to make sure that the bearing is facing the correct way before installation, if it has an encoder ring built into its inner seal. I have gotten into the habit of putting a paper clip on the encoder ring (it’s magnetic), making sure that I am assembling it in the correct manner with the encoder ring facing the ABS sensor. With the bearing encoder ring properly oriented and set square or straight to the knuckle, reassembly can begin. The new bearing must be pressed on the outer ring and not to the inner ring, or bearing damage can result. If it doesn’t start in straight, you must stop and reposition it or bearing damage will result.
Over-pressing into the knuckle can also cause damage. It just needs to be seated against the inner retainer area. After seating the bearing, a new snap ring retainer should be reinstalled into the clean retainer groove. Once the snap ring is installed, it is time to reinstall either a new flange or the carefully inspected old flange.
When installing the flange, the opposite side of the bearing must be supported to prevent the bearing from coming apart and again causing damage. The last step is to properly torque a new axle nut to the correct manufacturer’s specifications using a torque wrench... not an impact gun. The Gen 1 and other bearings are susceptible to damage from the use of an impact gun, both from tightening the axle nut and during the installation of the bearing into the knuckle without the proper tools. Industry experts stress that the leading cause of premature Gen 1 bearing failure is the failure to properly torque the axle nut, even after careful installation.
The Gen 2 wheel bearing design
The Gen 2 wheel bearing design uses a greased and sealed-for-life double row angular contact ball bearing set comparable to the Gen 1 design, but the outer race is now integrated into the flange on the Gen 2 design. This integration lowers the weight of the bearing assembly, something the manufacturers favor as they continually look for ways to reduce vehicle weight. The flange will have the spigot or pilot to locate the rotor/drum/wheel assembly, the studs or threaded holes to attach the wheel and, if needed, an ABS tone ring or encoder imbedded inner seal. The Gen 2 wheel bearing assembly can be found on the non-driven front wheels or on the non-driven rear axle of a vehicle. It will be mounted to a machined spindle, and held in position by a retaining nut.
Repairing or replacing a Gen 2 wheel bearing can be straightforward and normally requires the removal of the rotor, caliper bracket or the brake drum, dust cover and the axle retaining nut. Occasionally a slide hammer or puller may be required to remove the assembly, but care must be taken not to damage the threads on the spindle or the spindle itself.
When reassembling, all the mating surfaces and the spindle should be cleaned and lubed with the recommended lubricant, typically a small amount of engine oil.
It’s important to note that never-seize lube should not be used, as it may interfere with the bearing seating properly and the proper axle nut torque may not be achieved. During reassembly, a new axle nut and dust cap are required by most manufacturers. Again, don’t be tempted to use an impact gun. A torque wrench must be used to properly tighten the axle nut to the manufacturer’s specifications to prevent premature wheel bearing failure.
The Gen 3 wheel bearing design
The Gen 3 wheel bearing design incorporates two separate flanges and a double row angular contact ball bearing design that are sealed and lubed for life. The use of two flanges simplifies suspension and knuckle design and creates a compact unit. The outer flange doesn’t rotate and is attached to the knuckle or suspension via a machined surface with mounting provisions (bolts or threaded holes). The inner rotating flange will incorporate the spigot and the threaded holes or studs to locate and retain the wheel. The Gen 3 unit is used in both driven and non-driven applications, but if it is being used on a driven-wheel application, the inner ring will now have splines to transfer torque to the wheel from a splined driveshaft. A sensor for the TCS, ESP or ABS systems may also be incorporated into the design of the Gen 3 unit.
Servicing a Gen 3 unit requires removing the necessary brake parts and pieces and in some cases the axle shaft to gain access to the hardware retaining the inner flange to the suspension or knuckle. There are several tools available to remove these units if they have become frozen or seized to their mounting surface. Care must be taken not to damage the mating surfaces involved, especially the knuckle or the spindle, with the use of composite lightweight alloys and materials.
Before installing the replacement unit, the mating surfaces should be clean and free of any rust, debris, nicks or defects. When installing the new hub assembly onto its mounting surface, it is critical that it is aligned and seated properly and that any torque-to-yield fasteners involved are replaced before being torqued to the manufacturer’s specification. If an axle nut is used it must also be properly torqued again without the use of an impact gun.
Like the Gen 1 and 2, the Gen 3 is susceptible to improper torqueing of the axle nut if an impact gun is used.
Doing it right the first time
The use of a double row angular contact bearing assembly has become the norm. They require less space, are cheaper, allow for simplified suspension design and can deal with the axial and radial loads that are placed on them. However, they can and do fail and will need replacement.
A range of factors can cause a wheel bearing failure; age, curb contact, moisture intrusion, oversize tires, worn suspension components, out-of-balance wheels, and the operating conditions of the vehicle, to cite just a few examples. But today’s sealed wheel bearings are durable and some aftermarket bearing suppliers have even developed specialized Gen 3 bearing assemblies for SUVs and trucks to improve the initial design. Their revised design uses a larger diameter outer bearing containing more ball bearings compared to the inner bearing.
This design creates a stiffer unit that offers several benefits; it reduces NVH (noise/vibration/harshness), increases brake rotor life due to lower lateral flange runout, and improves the vehicle’s steering/handling characteristics.
But even the best replacement wheel bearing can fail prematurely if a torque wrench isn’t used on the axle nut to set the proper bearing end play and preload. But proper torque isn’t the only essential to proper bearing replacement. Debris-free surfaces, proper bearing orientation, proper tools for removal and installation, the replacement of required fasteners and the careful attention to the routing of ABS harnesses will prevent comebacks and contribute to a successful repair. ■
I would like to thank Neil Hogan of SFK USA Inc. and Matt Gorski of NTN Bearing Corp. of America for their help and contributions in preparing this article.
Jeff Taylor boasts a 32-year career in the automotive industry with Eccles Auto Service in Dundas, Ontario, as a fully licensed professional lead technician. While continuing to be “on the bench” every day, Jeff is also heavily involved in government focus groups, serves as an accomplished technical writer and has competed in international diagnostic competitions as well as providing his expertise as an automotive technical instructor for a major aftermarket parts retailer.
To read more from Jeff Taylor, see:
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