Introduction
Rolling bearing catalogues publish dynamic load rating, static load rating and rated life values. Understanding these terms is essential before comparing sizes or requesting a quotation.
This guide explains load rating concepts at methodology level. It complements the Industrial Bearing Selection Guide. Numerical ratings, life calculations and application factors are manufacturer-specific — confirm on the relevant type authority or catalogue before ordering.
Dynamic vs static ratings
| Term | Typical definition | Selection relevance |
|---|---|---|
| Dynamic load rating (C) | Load under which the bearing attains a defined rated life at reference speed (ISO 281 basis) | Primary basis for size selection against required life |
| Static load rating (C0) | Load causing permanent deformation above a defined limit | Safety check for stationary, shock or very low-speed overload |
| Reference speed | Speed associated with standard rating conditions | Context for life calculation; not always the limiting speed |
| Limiting speed | Maximum speed for reliable operation with given lubrication and clearance | Must not be exceeded without manufacturer confirmation |
Dynamic rating assumes proper mounting, lubrication and operating conditions. Static rating matters when the bearing is stationary under load, subjected to shock, or rotates at very low speed.
Equivalent load
Real applications rarely apply pure radial or pure axial load. Catalogues use an equivalent dynamic load that combines radial and axial components according to the bearing type and contact angle.
| Concept | Purpose |
|---|---|
| Radial load (Fr) | Force perpendicular to the shaft axis |
| Axial load (Fa) | Force parallel to the shaft axis |
| Equivalent load (P) | Single load value used in life calculation for combined loading |
The formula relating Fr, Fa and P is bearing-type-specific. Deep groove ball, angular contact, tapered and spherical types use different factors. Use the manufacturer's calculation method for the bearing being selected — do not transfer factors between types or brands.
L10 bearing life
L10 life (basic rating life) is the life that 90% of a bearing group is expected to reach or exceed under defined conditions. It is expressed in millions of revolutions or hours.
| Term | Meaning |
|---|---|
| L10 (basic rating life) | Life at 90% reliability under reference conditions |
| L10h | Basic rating life expressed in operating hours |
| Modified rating life | Life adjusted for lubrication, contamination and reliability factors where manufacturer methods allow |
Life calculation requires:
- Equivalent dynamic load (P) — from application loads and bearing type factors.
- Dynamic load rating (C) — from catalogue for the candidate size.
- Speed — to convert revolutions to hours if needed.
The basic relationship is proportional to (C/P) raised to a life exponent that depends on bearing type (commonly 3 for ball bearings and 10/3 for roller bearings in standard ISO treatment). Use the manufacturer's published exponent and calculation tools for the specific bearing.
This guide does not publish numerical life values or universal application factors.
Using catalogue data
When reviewing a type authority or manufacturer catalogue:
| Data field | What to verify |
|---|---|
| Dynamic load rating (C) | Continuous duty basis for the published size |
| Static load rating (C0) | Stationary or shock overload check |
| Limiting speed | Maximum operating RPM for the size and lubrication |
| Reference speed | Context for standard life rating |
| Bore / OD / width | Physical fit in the assembly |
A bearing size that satisfies life on paper may still be unsuitable if speed, clearance, fit or sealing limits are exceeded. Review all governed fields together.
Selection workflow
- Establish application loads — radial, axial and combined; note shock or reversing duty.
- Calculate equivalent dynamic load — using manufacturer factors for the shortlisted type.
- Define required life — plant standard or machine design target in hours or revolutions.
- Shortlist bearing type — via Industrial Bearing Selection Guide.
- Compare catalogue C values — for candidate bore sizes.
- Verify static load and speed — against C0 and limiting speed.
- Confirm clearance and fits — see clearance and fit guide.
- Request engineering confirmation — send duty data through engineering enquiry.
Next steps
- Review the industrial bearings category and open the relevant type authority.
- For full selection context, read the Industrial Bearing Selection Guide.
- For designation decoding on existing bearings, read How to Read Bearing Designations.
- Send load, speed and life requirements for engineering review.
Scope and limitations
- This article provides general load rating definitions only; catalogues own numerical data.
- Life calculation methods, exponents and application factors are manufacturer-specific.
- Do not assume one manufacturer's rating basis applies to another brand.
- Golden Bearing Company does not publish invented load ratings or guaranteed interchange equivalence.