Thinking About Using an Economy Hub Unit?

Thinking About Using an Economy Hub Unit?

Sponsored by BCA Bearings by NTN

Thinking About Using an Economy Hub Unit? Here are three applications that will change your mind.

There are applications you do not want to take chances when replacing a hub unit. Using an economy hub unit can often result in a comeback and unhappy customer. The failures can typically be attributed to low-quality materials, outdated manufacturing processes, or even bad catalog management.

Materials matter when it comes to wheel bearings. As for the raw steel, the specifications are very tight for hardness and ductility. OE-quality bearing manufacturers will use very clean steel free from contamination that can cause inclusions. These inclusions can cause breaks and cracks in the raceways and even compromise the structural integrity of the castings. 

Even the materials used for the seals matter. OE-quality hub unit manufacturers will use seal materials that are far from just rubber. These advanced elastomeric materials enable the seal to keep the grease in and contaminants out. These materials and designs also lower the drag and friction between the seal and bearing surfaces.

How bearings are manufactured has evolved in the past 25 years, especially for gen three and four hub units. New casting, forging and machining methods have improved the quality and functionality of hub units. These technologies can include new ways to heat-treat components or setting the preload of the final product. 

Some economy hub unit manufacturers might try other methods to match the original part, which could shorten the life of the hub unit on the vehicle. A prime example of this is orbital forming. This cold rolling process uses axial and radial forces to form a flange that sets the preload for the assembled hub. If the rolling of the flange is not performed properly, it can cause damage to the bearing and seals. Also, if not correctly performed, it can cause cracking of the flange and stub axle.

Another way some economy hub units can cost you is the way they manage their catalog of applications. When a vehicle platform is designed, it could have multiple engine and drivetrain options. Also, the OE might make changes every model year that could impact the hub units. These could be slight changes like the length of the wheel speed sensor harness, the number of magnets on the encoder ring, or even changes to the rolling elements and raceways. 

An economy hub unit brand might look to consolidate part numbers and applications. To do this, they will look for commonalities applications share. You have probably experienced this when the replacement unit has a too short wheel speed sensor harness, or the new unit causes a code for an erratic wheel speed sensor signal. 

In these cases, the brand puts its profitability over the engineering of the final product. Close enough is not good enough when it comes to hub units.

You might think this is all propaganda. But below are three real-world examples of applications where an economy hub unit can cause you a comeback.

Audi B6 (A3 and A4)

When you remove a wheel, you expect to see an axle nut on a shaft. But, on the 2002-2009 Audi A4, you will see the hex of a 17mm bolt. This hub unit for the B6 platform uses a different method to set the preload on the bearing. Instead of an axle and nut, these units use a torque-to-yield bolt to secure the wheel flange to the drive axle. 

The metallurgy and design of the bolt allow it to stretch to increase the clamping loads. The torquing procedure involves tightening the bolt to 140-ft/lbs and then turning the bolt an additional 180 degrees. Some economy wheel bearing sets will not include the bolt, or the one in the box is not up to specifications. If the old bolt is reused, the clamping loads might be reduced, and the bolt might snap during installation or while driving. This hub unit is also secured to the knuckle using four torque-to-yield bolts.

When you order a BCA W60673 hub unit, you get a new torque-to-yield flange bolt and four new bolts to secure the hub unit to the knuckle.

Ford IWE

One of the most challenging applications for hub units can be the 2015 and newer Ford F-150. You do not want to take a chance with the trucks because there are five different options for the bearings depending on the model year. You have the typical variations for V6 and V8 models. There are other hub unit variations for 2WD and 4WD models. If that wasn’t bad enough, there are also special models like the Raptor.

Some economy hub unit manufacturers will try to consolidate the part numbers by creating parts that fit multiple models and options. With this approach, they might undersize the bearings or have a wheel speed sensor harness that might be too long or short for some applications. 

4WD models use the Ford Integrated Wheel End (IWE). You will notice differences from other applications when you remove the old unit. The first thing you will see is a gear or splines on the inboard side of the hub unit. The gear’s splines match the one found on the end of the CV joint and inside the actuator. 

The splines are precision machined to smoothly engage the clutch ring housed in the actuator. The gear on the hub unit is held in place using orbital forming. If you look inside the bore of the hub unit, you will notice two bearings. The first bearing is a needle roller bearing that supports the shaft. Near the wheel flange and axle nut is a sealed ball bearing.


Tesla Model S, X and 3

Economy hub unit manufacturers might have problems with the orbital forming process. This can damage the bearing and the cog on the end of the hub unit. This can result in a noisy hub unit in 2WD and 4WD operation. 

The front and rear wheel hubs for all Tesla models are not that much different from most hub units for internal combustion powered sedans and trucks. The hub unit does not use exotic materials or non-conductive wheel bearing grease. The installation procedure is identical to many other vehicles, with four bolts attaching the hub unit to the knuckle and an axle nut to secure the outer CV joint.

What makes this application sensitive to low-quality wheel bearings is the performance and how the preload is set at the factory by Tesla. All models use a gen three hub unit that utilizes orbital forming. This process requires precision and powerful presses. If the preload is not set correctly with orbital forming, the rolling elements and races will not align properly and cause the hub unit to wear prematurely. Eventually, the wear will cause noise problems, and the air gap for the wheel speed sensor will change resulting in a wheel speed sensor code.

The other reason you do not want to take chances with an economy hub unit for any Tesla vehicle is the performance. The electric motor can deliver instant torque and a 0-60 time in under five seconds or less for all models. 

The other factor is weight. All Teslas weigh more than 4,000 lbs. This weight only increases if the Tesla has the optional extended-range battery or dual motor. This puts even motor stress on the hub unit. 

What makes it worse is the quiet electric motor. If a hub unit starts to make noise, the customer will notice. Taking a chance with an economy hub unit for a Tesla might cost you a comeback and a potentially lucrative customer.

Hub units are highly-engineered components and are difficult to reverse engineer and even more challenging to replicate some manufacturing processes. They are also safety-critical components that keep the wheel on the vehicle and contain sensors utilized by ABS, stability control and ADAS systems. Taking a chance with an economy hub unit might save the customer a few bucks, but it could cost you even more.

This Article is Sponsored By: BCA Bearings by NTN

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