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A Comprehensive Guide to Different Types of Fan Bearings

Fan bearings come in different quality levels and with different life spans. We shed some light on the details and why we are using which bearings for our fans.

Fan bearings come in many different shapes and sizes. Each type of bearing has its own advantages and disadvantages. For example, sleeve bearings are inexpensive, but have a short life and poor noise profile. Fluid dynamic bearings have a longer lifespan and a better noise profile. It is important to choose the right type of fan bearing for your application and budget, to ensure optimal performance and longevity. We discuss the most important bearing types, but will leave out some exotic types such as hydrostatic bearings and hybrid solutions, which are either very expensive to manufacture or simply not relevant enough for computer fans.

The gold standard: Fluid dynamic bearing (hydro dynamic bearing)

If the best is what you need, try fans with fluid dynamic bearings (FDB). Due to the rotation of the shaft in the bearing, they dynamically build up a very thin film of pressurized fluid. Bearing and shaft do not come into direct contact with each other and spin with no friction on the lubricant. As a result, they practically do not wear out. Fluid dynamic bearings require extremely precise manufacturing processes, which is reflected in the somewhat higher cost.
Their life expectancy is unmatched and is estimated at about 300,000 hours. They are also very quiet and can be mounted in any orientation, without concern for degradation. 
We use fluid dynamic bearings for our top-of-the-line fan series Silent Wings 4.

The reliable choice: Ball Bearings

Ball bearings are another popular option for fan bearings. They consist of small beads that reduce friction between the two surfaces, resulting in an extended lifespan and decent noise levels. Ball bearings can last for about 60,000 to 75,000 hours, making them a reliable choice. They are versatile and can be mounted in various orientations but may be slightly noisier than fluid dynamic bearings.

The budget-friendly option: Sleeve Bearings

Sleeve bearings are a cost-effective choice. They utilize a sleeve made of a low-friction material, and the fan shaft slides within this sleeve. Sleeve bearings have a lifespan of around 30,000 to 40,000 hours, and while they are generally quieter at the beginning of their life, the noise levels tend to increase over time as the bearing wears down. They are also sensitive to orientation, with vertical mounting being the most favorable for longevity.
Sleeve bearings can be found in the fans of our budget power supply series System Power and small form factor SFX L Power.

Combining the best of both: Rifle Bearings

Rifle bearings are an improved version of sleeve bearings, designed to combine the advantages of sleeve and ball bearings. They have a spiral groove on the interior of the sleeve, which helps to distribute lubricant evenly and reduce friction. This results in a longer lifespan (around 80,000 hours) and better noise performance compared to standard sleeve bearings. Since the fluid is pumped from a reservoir, lubrication is not affected by the fan’s orientation, so they can be mounted horizontally, vertically, or at an angle without negative effects on longevity or noise.
The Light Wings, Shadow Wings 2 and Pure Wings 2 fan series all use rifle bearings.

We hope this overview was interesting. We have published more articles on our blog discussing fan technology and features, such as pulse width modulation (PWM) and the 6-pole motors and interchangeable mounting corners that are deployed with the Silent Wings fans. We also recommend checking out our comprehensive fan guide to learn more about be quiet! fans and their use-cases.