How to Choose the Right Bearing? 7 Key Factors That Affect the Correct Selection

Choosing the right bearing does not depend only on its dimensions. Two bearings of the same size can behave completely differently in the same application due to their design, internal clearance, sealing or material. An incorrect choice can cause increased friction, overheating, vibration, faster wear and, in the worst case, premature machine failure.

When making a selection, the bearing should therefore always be considered as part of the complete mechanical system. Below, we present seven factors worth checking before making a choice.

1. Type and magnitude of load

The first question is what forces the bearing will have to accommodate. Loads are mainly divided into radial loads, which act perpendicular to the shaft axis, and axial loads, which act along the axis. In many applications, both occur at the same time.

Ball bearings are highly versatile and suitable for many combinations of loads, while certain types of roller bearings are often more appropriate for higher radial forces. For more pronounced combined loads, designs intended to accommodate axial forces more effectively can also be considered.

Not only the maximum force is important, but also how it changes during machine operation.

2. Rotational speed

Every bearing has a speed range within which it can operate reliably. As rotational speed increases, friction, heat generation, lubrication and manufacturing accuracy become increasingly important.

A bearing that operates without difficulty at low speeds is therefore not necessarily suitable for a high-speed electric motor or another application with very high rotational speeds.

For more demanding applications, the cage design, the lubricant used and the sealing method must also be taken into account.

3. Operating temperature

Temperature affects bearing service life, lubricant properties and the dimensional behaviour of individual components.

At higher temperatures, the shaft, housing and bearing itself undergo thermal expansion. This can change the bearing's internal clearance. If these changes are not taken into account during design, increased friction, heating and wear may occur.

For temperature-demanding applications, special bearing designs and suitable high-temperature lubricants are also available.

4. Dust, moisture and other contaminants

The working environment often determines what level of protection the bearing requires.

Requirements in a clean and enclosed environment differ from those in manufacturing, agricultural machinery or other systems where dust, water and various particles are present.

Two common designations are 2RS and ZZ. A 2RS design uses rubber seals on both sides and provides better protection against the ingress of contaminants and moisture. ZZ indicates metal shields, which provide a different balance between protection and friction.

The choice is therefore not about which design is generally better, but which one is more suitable for the specific conditions.

5. Internal bearing clearance

One often overlooked parameter is internal bearing clearance. It describes the possible relative movement of the inner and outer rings before the bearing is installed and loaded.

The designation C3, for example, indicates increased internal clearance compared with the normal design.

This does not mean that C3 is automatically of higher quality or more suitable. Increased clearance is useful in applications where temperature, installation method or other factors reduce the actual clearance during operation.

6. Lubrication

Even a correctly selected bearing can fail much sooner if bearing lubrication is inadequate.

Lubricant reduces friction and wear, helps dissipate heat and protects surfaces against corrosion. The main factors to consider when selecting a lubricant are speed, load, temperature and environmental conditions.

The problem is not only too little lubricant. Excessive amounts can also increase resistance and cause additional heating. The correct lubricant type, quantity and relubrication interval are therefore all important.

7. Installation and the complete bearing arrangement

Bearing service life does not begin only when the machine is first started. Its performance is strongly influenced by correct bearing installation.

Incorrect installation force, improper fit, shaft misalignment or damage to the raceways can shorten the service life of even a high-quality bearing.

In addition to the bearing, the shaft, housing, fastening method, sealing, lubrication and operating conditions must therefore be checked. Only the combination of all these factors represents properly designed bearing technology.

The right bearing is determined by technical requirements, not dimensions alone

Standard designations such as 6201, 6204 or 6205 allow quick identification of the basic design and dimensions, but the designation alone does not tell us everything we need to know before making a selection.

At M&M Intercom, when selecting bearings and bearing technology, we therefore consider the actual operating conditions: loads, speeds, temperature, environment, required clearance, lubrication method and the design of the complete assembly.

A correctly selected and installed bearing can mean longer machine service life, less vibration, fewer unexpected stoppages and lower maintenance costs. In more demanding applications, a technical assessment before selection is generally far less costly than dealing with the consequences of an incorrectly selected bearing.