2311 bearing: complete specifications & equivalents
The 2311 is a ISO 15 radial bearing sized 55 x 120 x 43 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 43 mm |
| Seal / shield | open |
| Basic dynamic load rating C | 76.5 kN |
| Basic static load rating C0 | 24 kN |
| Fatigue load limit Pu | 1 kN |
| Limiting speed (mechanical) | 4800 rpm |
| Mass | 2080 g |
| Manufacturer designation | 2311S |
| Standard | ISO 15 |
| Catalog version | CAT. No. 2203-3/E 2024 |
| Last verified | 2026-09-25 |
Source: catalog reference (CAT. No. 2203-3/E 2024) · extracted 2026-09-25
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (CAT. No. 2203-3/E 2024); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & 2300-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.693 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 mm |
| Smallest bore in 2300-series | 10 mm |
| Largest outer diameter in 2300-series | 215 mm |
| Width range across 2300-series | 17–73 mm |
| Bore position in 2300-series (smallest first) | 12 of 21 |
| Bore above smallest 2300-series size | 45 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 2311 model number is decoded
In the 2300-series (ISO 15 dimension series) the leading digits 23 mark a double-row self-aligning ball bearing and the last two digits encode the bore: 2311 carries bore code 11 = 55 mm. Outside diameter 120 mm and width 43 mm follow the ISO 15 general plan. The cylindrical bore fits directly on a machined shaft seat; a tapered-bore K variant is available for adapter-sleeve mounting. Two rows of balls run on a common sphered outer raceway, allowing the inner ring to pivot and compensate for shaft deflection or housing misalignment.
Typical equipment & failure modes
Common applications
- paper mill and processing equipment shafts
- industrial electric motor shafts
- pump and compressor drive shafts
- gearbox and speed reducer shafts
Known failure patterns
- contamination wear from dust and dirt ingress through the open arrangement
- lubricant starvation when no regreasing interval is maintained
- false brinelling from vibration while the shaft is stationary
- edge loading and stress concentration from excessive misalignment beyond the allowable angle
Selection pitfalls — read before you substitute
- Temperature rise and interference fits consume internal clearance on this 55 mm bore: a CN bearing on a tight, hot shaft can lose all residual clearance — size 2311 with C3 for those conditions.
- The 23xx heavy wide-section at 55 mm bore is built for high-load, lower-speed duty; specifying it in a high-rpm application gives excess heat and short grease life — use 12/13 there.
- The open 2311 has no lubricant retention: grease escapes and contaminants migrate straight into the 55×120×43 mm raceway, so specify a sealed arrangement for dusty or washdown duty.
- Open bearings tolerate the highest speeds in the 2300-series but need a defined regreasing interval; run-to-failure lubrication is the dominant cause of early failure in open 2311 units.
- Self-aligning ball bearings have lower axial load capacity than same-size angular-contact or tapered-roller bearings; verify the axial component is within the Y-factor limits for 2311.
Frequently asked questions
What are the dimensions of a 2311 self-aligning ball bearing?
A 2311 self-aligning ball bearing has a 55 mm bore, 120 mm outer diameter and 43 mm width, per ISO 15 boundary dimensions. This is the cylindrical-bore version; a tapered-bore K variant is available for adapter-sleeve mounting.
How does the 2311 bore code work?
The last two digits of 2311 are bore code 11, giving 11 × 5 = 55 mm bore. The 120 mm outside diameter and 43 mm width follow the ISO 15 diameter series, not the bore code alone.
What does the open suffix mean on 2311?
A bare 2311 designation means open: no shields or seals, normal CN radial clearance and P0 normal tolerance unless further suffixes are ordered. The application must supply and retain the lubrication.
How does the 2300 compare with other self-aligning series at the same 55 mm bore?
The 23xx is the wide heavy section: 120×43 mm, 32.5 mm radial section at 55 mm bore — the highest-capacity double-row self-aligning option here, aimed at lower-speed, high-load shafts.
Reviewed & verified by the MPN Base engineering desk against source catalog CAT. No. 2203-3/E 2024 on 2026-09-25. Read our editorial & correction policy.