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Selecting Bearings for Combined Loads: 2026 Engineer's Guide

Selecting Bearings for Combined Loads: 2026 Engineer's Guide

Combined loads occur when machinery experiences both radial and axial forces simultaneously, requiring specific components like tapered roller, spherical roller, or angular contact ball bearings. Choosing the right bearings for combined loads ensures your industrial machinery operates efficiently without premature failure. A radial load acts perpendicular to the shaft, while an axial load pushes parallel to it. When these forces combine, maintenance engineers must select a bearing engineered to distribute both force vectors effectively.

At HI-TEC BEARINGS, our team provides expert technical support and precision components to help manufacturers optimize equipment. This guide explores load capacity, speed limits, and misalignment tolerance, comparing bearing types and explaining how to calculate equivalent dynamic bearing loads.

What is the difference between a radial load and an axial load?

Radial loads act perpendicular to the shaft, while axial loads act parallel to it; combined loads require bearings engineered to distribute both force vectors. Combined loads occur when machinery experiences both radial and axial forces simultaneously, requiring specific components like tapered roller, spherical roller, or angular contact ball bearings[1][2].

A radial load acts at a 90-degree angle to the bearing axis, stressing the outer diameter and raceways[3][1]. The weight of a rotating wheel acting downward on its hub is a standard example[4]. Conversely, an axial load - also known as a thrust load - acts along the bearing axis, pushing or pulling the assembly parallel to its centerline[3][5]. You see axial loads in gearboxes, helical gears, and screw jacks[1][2].

In industrial applications, bearings rarely encounter pure radial or axial forces. External load vectors resolve into simultaneous radial and axial components[1][6]. The rolling elements carry these concurrent forces, altering stress distribution within the contact patch even when one load type dominates[1][7]. To handle these simultaneous forces without suffering rapid wear or brinelling, engineers rely on purpose-built angular contact ball bearings or specialized roller bearings.

How do I choose a bearing by load and speed?

Selecting the right bearing requires balancing the application's maximum operating speed with its combined radial and axial load requirements. Angular contact ball bearings support high RPM speeds, while tapered roller bearings are engineered to handle heavy combined loads at lower rotational speeds[8][9].

When evaluating bearings for combined forces, maintenance engineers must cross-reference load capacity against the frictional heat generated at operating speeds. Angular contact ball bearings utilize point contact, reducing friction and allowing speeds up to 1.5 times faster than comparable roller bearings[8]. However, point contact limits load-carrying capacity. In contrast, tapered roller bearings utilize line contact, delivering substantially higher radial and axial load ratings - often 1.5 to 3 times the dynamic load rating of a ball bearing at the same size[8][9].

Selection Criteria Angular Contact Ball Bearings Tapered Roller Bearings Spherical Roller Bearings
Speed Capability High - minimal friction[8] Low to moderate - higher heat[8] Low to moderate - friction-heavy
Combined Load Capacity Moderate - lower loads[10] High - rigid support[9] High - heavy radial/axial forces
Primary Advantage Precision and high RPM[11] Maximum rigidity[12] Misalignment tolerance

If machinery requires extreme rotational velocities, prioritize angular contact ball bearings. If the application demands unyielding rigidity under immense pressure, tapered roller bearings provide necessary structural integrity.

Tapered vs spherical roller bearing - which should I use for heavy loads?

Spherical roller bearings are the optimal choice for heavy combined loads when the application requires tolerance for shaft misalignment. Tapered roller bearings offer superior rigid support for heavy combined loads but require precise alignment to prevent premature wear[13][14].

Internal geometry dictates how these bearings handle housing distortion and shaft deflection.

Evaluate your machinery's structural rigidity before selecting; prioritizing stiffness over alignment tolerance in a flexing system will cause rapid bearing failure.

How do I calculate the equivalent dynamic bearing load?

Maintenance engineers must calculate the equivalent dynamic bearing load to accurately compare the lifespan of these three bearing types under combined forces. The calculation combines radial and axial forces using specific vendor-provided factors (X and Y) to determine a single representative load value[17][18].

The ISO 281 standard defines the equivalent dynamic bearing load (P) as the purely radial load yielding the same bearing life as the actual combined forces[17][19]. Because bearings experience simultaneous stresses, you cannot use basic catalog ratings without adjusting them.

  1. Identify external forces: Determine the actual radial load (Fr) and axial load (Fa) acting concurrently[17].
  2. Determine the limiting ratio (e): Consult the manufacturer's catalog to find the limiting value (e). This threshold dictates if the axial load is significant enough to impact the calculation[18][20].
  3. Select X and Y factors: If the axial-to-radial load ratio exceeds the threshold (e), locate the radial load factor (X) and axial load factor (Y) in the catalog[18][21]. Deep groove ball bearings under significant axial load often use an X factor of 0.56[22][23].
  4. Calculate equivalent load: Apply P = X(Fr) + Y(Fa). This single load value (P) is used in standard fatigue life equations to predict bearing survival[17][24].

Frequently Asked Questions

What is the difference between a radial load and an axial load?

A radial load acts perpendicular to the bearing axis, like the downward weight of a vehicle on a wheel hub[3][1]. An axial load acts parallel to the bearing axis, pushing along the shaft, as seen in screw jacks[3][5].

Tapered vs spherical roller bearing - which should I use for heavy loads?

Use spherical roller bearings if machinery experiences shaft deflection, as they tolerate 0.5 to 2 degrees of angular misalignment[15][14]. Use tapered roller bearings when the shaft is perfectly aligned and you require maximum rigidity[9][13].

How do I choose a bearing by load and speed?

Select angular contact ball bearings for high-speed applications with moderate loads, as point contact minimizes friction[8][10]. Choose tapered or spherical roller bearings for heavy combined loads at lower speeds, as line contact supports greater forces[8][9].

How do I calculate the equivalent dynamic bearing load?

Use the ISO 281 formula: P = X(Fr) + Y(Fa). Multiply your actual radial load (Fr) by the catalog's radial factor (X), and add it to your actual axial load (Fa) multiplied by the axial factor (Y)[17][18].

References

  1. Understanding Bearing Loads in Mechanical Systems. https://www.tpibearings.co/technology/understanding-bearing-loads/ (2025-05-09)
  2. How Do I Determine the Loads on a Bearing? - Pibsales. https://pibsales.com/bearings/how-do-i-determine-the-loads-on-a-bearing/ (2025-06-16)
  3. Loads | SKF. https://www.skf.com/us/products/plain-bearings/spherical-plain-bearings-rod-ends/principles/selecting-bearing-size/loads
  4. Understanding Axial and Radial Loads: Key Differences and .... https://www.tpibearings.co/technology/axial-load-vs-radial-load-2/ (2025-03-31)
  5. What is Axial Load and Radial Load? - NBC Bearings. https://www.nbcbearings.com/what-is-axial-load-and-radial-load/ (2024-02-20)
  6. How axial and radial loads affect linear motion systems. https://www.linearmotiontips.com/how-axial-and-radial-loads-affect-linear-motion-systems/ (2021-11-10)
  7. Analysis of preloaded bearings under combined axial and radial .... https://www.sciencedirect.com/science/article/abs/pii/0890695594900353
  8. Roller Bearings vs. Ball Bearings: What's the Difference?. https://pibsales.com/bearings/roller-bearings-vs-ball-bearings/ (2026-03-05)
  9. Expert Insights & Hands-On Tips for Tapered Roller Bearings. https://medias.schaeffler.us/en/knowledge-center/rolling-bearings/tapered-roller-bearings (2013-01-01)
  10. What Are the Differences Between Bearings? The various types and .... https://koyo.jtekt.co.jp/en/bearing-column/bearing_trivia_1st_series/bearing_trivia_1st_series_04.html (2019-09-24)
  11. What is the Difference Between Ball & Taper Roll Bearing. https://bywbbearing.com/difference-between-ball-taper-roll-bearing/ (2024-05-28)
  12. Tapered Roller Bearings | NSK Global. https://www.nsk.com/products/roller-bearings/tapered-roller-bearings/ (2024-07-11)
  13. The tapered roller bearing - NTN Bearing Wizard. https://bearingwizard.com/rolling-bearing-types/tapered-roller-bearing/ (2022-03-09)
  14. Spherical roller bearings | Schaeffler medias. https://medias.schaeffler.us/en/knowledge-center/rolling-bearings/spherical-roller-bearings (2014-01-01)
  15. What is the misalignment tolerance of spherical roller bearings? - Blog. https://www.wxinggroup.com/blog/what-is-the-misalignment-tolerance-of-spherical-roller-bearings-2061077.html (2025-12-10)
  16. [PDF] Tapered roller bearings. https://dicksonbearings.ie/dbdocument/2394/Taper%20Roller%20Bearings.pdf
  17. [PDF] ISO 281 - iTeh Standards. https://cdn.standards.iteh.ai/samples/4193/9da53eac50eb4e798b1d69c514301f7b/ISO-281-1990.pdf (1990-12-01)
  18. [PDF] ISO 281-1:1977 - iTeh Standards. https://cdn.standards.iteh.ai/samples/4194/3941d425a13242dd8244664f709efda7/ISO-281-1-1977.pdf (1977-03-15)
  19. [PDF] Evolution of rolling bearing life rating through the standardization. https://stumejournals.com/journals/mtm/2020/6/222.full.pdf (2025-09-17)
  20. Load Ratings and Bearing Life - New Hampshire Ball Bearings, Inc.. https://www.nhbb.com/knowledge-center/engineering-reference/ball-roller-bearings/load-ratings-bearing-life (2026-06-26)
  21. Bearings - COMBINED Radial and Axial LOADS in 10 Minutes!. https://www.youtube.com/watch?v=3b8yOMSWXXk (2020-10-18)
  22. Equivalent Dynamic Load Calculator - ToolGrit. https://www.toolgrit.com/tools/equivalent-dynamic-load-calculator (2026-06-18)
  23. [PDF] DETERMINATION OF CERTAIN PARAMETERS OF A BEARING. https://www.mmscience.eu/journal/issues/june-2017/articles/determination-of-certain-parameters-of-a-bearing/download (2025-10-16)
  24. Rolling bearing life | MESYS AG. https://www.mesys.ag/?p=1340 (2013-09-10)