What is Bearing Clearance and Why is It Important?

When selecting bearings, clearance is one of the most important factors to get right. If the clearance is wrong, the bearing can fail early, run hot, or make noise. Proper clearance ensures smooth rotation and long life.

What Is Bearing Clearance?

Bearing clearance is the total distance one bearing ring can be moved relative to the other. In other words, it's the total space between the inner and outer rings of a bearing. As shown in the diagram below, there are two types of bearing clearance:

• Radial clearance (up-and-down movement)
• Axial clearance (side-to-side movement)

This small amount of space is critical for performance.

Why Do Bearings Need Clearance?

Most rolling element-style mounted bearings have some degree of internal clearance to:

• allow for free rotation of the inner ring;
• prevent metal-to-metal contact between rolling elements and raceways; and
• accommodate for thermal growth of internal components.

If the bearing clearance is not selected properly, it will affect bearing function and lifespan. If clearance is too tight, the bearing can overheat and wear out. If it’s too loose, the bearing may vibrate or misalign. Both shorten bearing life.

Bearing Clearance Classes

Clearance isn’t one-size-fits-all. ISO standards define five classes:

• C2 = smaller than normal
• C0 = normal clearance
• C3 = greater than normal
• C4 = greater than C3
• C5 = greater than C4

Which class you need depends on temperature, speed, load, and other conditions.

Why Bearing Clearance Matters in Tough Applications

Metal-to-metal contact within a bearing is never good. This type of contact leads to increases in operating temperature, noise and surface fatigue, which in turn leads to bearing failure.

In steel mills, bearings often run at 400°F (204°C) in furnace applications. At these temperatures, parts expand. Bearings with extra clearance prevent metal-to-metal contact and keep the system running.

How Regal Rexnord Bearing Brands Make It Easier

The Regal Rexnord Bearing Application Engineering can help you ensure the proper clearance range. This can help maximize performance and bearing life for your application. Mounted spherical roller bearings from brands like Rex and Link-Belt let you adjust clearance in the field. Just tighten or loosen a threaded cover. This eliminates the need for a specialized clearance bearing. This saves time and reduces lead times for custom parts.

This is just one of the key advantages our products offer to help reduce lead time for custom bearings.

The Regal Rexnord bearings portfolio features all classes of bearing clearance to fit your application needs. If you have questions or would like to talk to one of our application engineers, contact us below.

For more, visit Regal Rexnord's industry leading line of bearings products.