Wheel hub bearings connect the vehicle’s tires and axles, supporting the vehicle’s weight while smoothly transmitting rotational motion from the axle to the tires.
Since commencing production in the 1970s, NTN has continuously developed new products to meet evolving market demands. Among these, the “Low Rolling Resistance Hub Bearing” series—which achieves energy savings by reducing rolling resistance (Friction)—is currently in particularly high demand. In 2024, NTN launched the fourth and fifth generations of this series: the “Low Rolling Resistance Hub Bearing IV” (abbreviated as IV) and the “Low Rolling Resistance Hub Bearing V” (abbreviated as V). These bearings achieve up to approximately 64% lower rolling resistance compared to previous generations and improve electric vehicle power consumption by about 0.75%, making them highly anticipated in the market. How were these products developed? We interviewed two lead developers.
Achieving Further Low Rolling Resistance Through New Grease Development
In automobiles, the central metal component securing the wheel to the axle is called the hub, and the bearing used within it is known as the “hub bearing.” Hub bearings play a critical role in supporting the vehicle’s weight and smoothly transmitting the axle’s rotation to the tires. Since commencing production in the 1970s, NTN has continuously introduced new hub bearings tailored to evolving market demands. Against this backdrop, NTN developed the “Low Rolling Resistance Hub Bearing” in 2009, designed to reduce rolling resistance and enhance energy efficiency. This well-received product was subsequently serialized, with the fourth and fifth generations—‘IV’ and “V”—launched in 2024. The former updates the grease coating on the sealing section (detailed later) compared to the 2019-developed “Ⅲ” model. The latter further develops a new grease for the bearing interior. As a result, the “Ⅴ” achieves a maximum rolling resistance reduction of approximately 64% compared to its predecessor, improving electric vehicle power consumption by about 0.75% and extending single-charge range by 3 kilometers. “The new grease was developed through collaboration between our Development Department, the company’s Fundamental Technology Research Institute, and a grease manufacturer. By relentlessly pursuing low rolling resistance, we ultimately created a hub bearing that further reduces environmental impact,” stated Inazumi from the CVJ Axle Business Division Development Department, who led the “IV” development.
The Evolution of Hub Bearings and This Series
Hub bearings gained widespread adoption in the 1970s. After multiple evolutionary iterations and design changes, the current mainstream product is known as the third-generation hub bearing (GEN3). The first-generation hub bearing (GEN1) enhanced load capacity by connecting two single-row bearings in parallel, requiring external components to connect the hub to the vehicle body. The second-generation hub bearing (GEN2) integrated the bearing outer ring with the mounting flange. The third-generation hub bearing further consolidated hub components, achieving integration between the tire-side inner ring and the hub itself. Introduced in the late 1980s, the third-generation product gained widespread adoption and remains in use today.
The first generation of the low rolling resistance hub bearing series, designated “I,” debuted in 2009. Building upon the third-generation hub bearing structure, it featured an improved seal design and adjusted the curvature of the bearing raceway surface (the groove where balls roll), achieving a maximum 40% reduction in rolling resistance. Subsequent refinements included further sealing structure improvements (reducing contact points between seals and surrounding areas to lower rolling resistance while adopting labyrinth structures to prevent mud and water ingress) and optimized grease formulations (for both seal rings and bearing interiors). This led to the release of the improved “II” model in 2017 and the further optimized “III” model in 2019, featuring enhanced internal bearing grease. The “IV” and ‘V’ models developed in 2024 represent the latest iterations in this series. Nakajima from the CVJ Shaft Business Division Development Department stated: “Building upon the internal grease improvements in ‘III’, ‘IV’ optimized the sealing compound grease, while ‘V’ further upgraded the internal bearing grease. We remain committed to achieving the lowest possible rolling resistance at each stage.”
Although development of “IV” and “V” was slightly staggered, they proceeded in parallel—with Inao overseeing ‘IV’ and Naka managing “V.” Each team tackled the respective challenges of seal-applied and internal greases, iterating through trial and error to refine superior lubricant formulations.