Learn about the SKF hub unit evolution
When it comes to automotive performance, every component counts. This is especially true for the integrated hub unit, which helps keep your wheels attached to your vehicle, improves overall drivability and safety, and is critical to your anti-lock braking system (ABS) and the traction control system (TCS).
2024-04-01
SKF Hub Unit Evolution
SKF has led the way in wheel end innovation since the invention of the automobile, pioneering the concept of the pre-assembled unitized hub, as well as the integration of sensors to improve passenger safety and enhance car functionality.
To put the evolution of the design of SKF hub bearing units into better perspective, let’s take a deeper dive into the company’s portfolio of high-quality solutions:
Taper Roller Bearings:
SKF offers a wide range of tapers with pressed steel cages, manufactured to rigorous quality standards in both metric and inch sizes. With low cross sections and precise contact angles, these wheel bearings are designed to accommodate axial and radial loads when mounted with proper clearance.
Hub Bearing Unit 1 (HBU1):
Based on a double row angular contact ball bearing, HBU1 is optimized for the special operating characteristics encountered on car wheel applications. The unit offers specific support the moment a load is applied to the bearing during cornering. The main components, an outer ring and two inner rings, are matched with the ball set to give the correct clearance. The cages for the two ball rows are made from glass fiber reinforced polyamide. HBU1 is greased and sealed for life. Used mainly for driven wheels, HBU1 is also found in integral drum designs on the non-driven wheels of smaller cars.
Hub Bearing Unit 2 (HBU2):
Designed with the experience gained with HBU1, HBU2 has an outer ring with an integral flange, replacing the function of a separate hub. The flanged outer ring is designed as a lightweight structural component and the outer ring raceways are induction hardened for optimal bearing performance. The flange is tough, with threaded holes or studs and a spigot to center and mount the brake and wheel. The dimensions of the flange and spigot are designed to customer requirements. HBU2 is typically used with a rotating outer ring for non-driven front or rear wheels.
Hub Bearing Unit 3 (HBU3):
The third-generation hub bearing units carry a flange for the wheel and brake rotor attachment and a second flange for fixing the unit to the suspension. This fully integrated system provides significant simplification in corner design and handling when compared with more traditional designs. The dynamic load carrying capacity is maximized by using a separate inner ring for the inboard ball row. This inner ring is mounted with an interference fit and the outer ring flange is bolted to the suspension. The rotating inner ring, with its tough flange, spigot and threaded holes or studs, is designed for mounting the brake and wheel. HBU3 is also greased and sealed for life and used for both driven and non-driven wheel applications.
X-Tracker:
The X-Tracker series, the latest generation of SKF hub bearings, brings car-like handling and comfort characteristics to high-performance, light-duty truck and SUV applications. The newest design consists of a double row angular contact ball bearing arrangement, in which the outboard row is at a higher diameter and contains more balls than the inner row. This unique design increases the bearing’s capacity while improving hub stiffness by 50% over a traditional tapered bearing unit. A stiffer hub provides many benefits:
o Allows the wheel to run truer during cornering and acceleration.
o Reduces deflection of the hub face and wheel, which provides better steering, handling, and vehicle dynamic behavior.
o Reduces brake wear and tear, which helps reduce brake warranty costs.
o Improves both NVH (noise/vibration/harness) characteristics and bearing performance.
o Provides designers and systems integrators an alternative to a tapered bearing unit, allowing them to improve overall vehicle performance.
Today, over 80 million cars and light trucks worldwide are riding on SKF wheel bearings and hub units – more than all other brands combined. Next time you’re on the market for a new hub unit, install with confidence using an SKF solution.
Releated
2026-08-31
Seasonal heat, long-distance driving and heavier loads can accelerate wheel-end wear. A timely inspection can help catch the warning signs before they turn into costly downtime.
2026-07-31
When summer temperatures rise, vehicle components are pushed to work harder—and wheel-end bearings are no exception. While bearing failure rarely happens without warning, excessive heat is often one of the earliest signs that something in the system requires attention.
2026-06-30
As vehicle technology evolves, so do the skills required in the workshop. Increasing system complexity, electrification, and tighter tolerances mean that traditional training methods alone are no longer enough. To support the next generation of technicians, SKF Vehicle Aftermarket continues to invest in digital tools that bring learning closer to real-world conditions. One of the most innovative solutions in this space is the VR Training Garage. The VR Training Garage is designed to bridge the gap between theory and hands-on experience. Using virtual reality, technicians can step into a fully immersive workshop environment and perform procedures in a safe, controlled setting. From wheel-end inspections to bearing replacements, every step is guided, visual, and interactive—allowing users to learn by doing, without the risks associated with real vehicles.
2026-05-27
As peak travel season approaches, ensuring wheel-end reliability is essential for keeping vehicles on the road and operating efficiently. Winter driving conditions, marked by moisture, road salt, and fluctuating temperatures, can accelerate wear on critical components, especially bearings. A proactive inspection strategy before summer mileage ramps up can help fleets and service professionals avoid costly downtime.
2026-04-30
In today’s automotive aftermarket, efficiency and sustainability are essential. While bearings and major components often receive the most attention during maintenance, sealing solutions are sometimes overlooked. However, seal condition plays a critical role in vehicle efficiency, and component protection.
2026-03-31
In the world of wheel-end maintenance, few topics generate more confusion than the difference between seal seepage and seal leakage. Both involve the presence of lubricant outside its normal containment, but the implications for wheel-end health are very different. Understanding what you’re seeing—and why it’s happening—can help prevent unnecessary part replacements, ensure fleet uptime, and protect the long-term performance of the entire wheel-end system.
2026-02-27
Winter is one of the most demanding seasons for vehicles and for the sealing solutions that protect critical components. Cold temperatures, moisture and road salt combine to accelerate seal wear and can lead to premature failure if not properly managed. Understanding why seals fail in winter helps technicians prevent costly breakdowns, comebacks and customer dissatisfaction.
2025-05-19
In the ever-evolving world of technical training, staying ahead of the curve is crucial. Enter the SKF MechMaster VR Edition, a promising virtual reality (VR) experience designed to revolutionize the way mechanics and technicians approach mechanical systems. Developed by SKF Vehicle Aftermarket, the global leader in chassis and powertrain solutions, this VR tool offers an immersive and interactive platform for learning, training, and problem-solving
2024-05-28
The braking system is one of the most critical components of a vehicle and has a direct impact on safety. Among the various elements within this system, brake pads are crucial. They ensure that the vehicle stops safely and effectively, making the choice of high-quality pads essential. With more than a century of experience, SKF excels in the development of OE and Aftermarket solutions, including brake rotors with integrated bearings, and offers nearly 900 different brake pad sets for different applications.