32311CU bearing: complete specifications & equivalents
The 32311CU is a ISO 355 radial bearing sized 55 x 120 x 45.5 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 | 45.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 204 kN |
| Basic static load rating C0 | 252 kN |
| Fatigue load limit Pu | 30.5 kN |
| Limiting speed (mechanical) | 3100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2470 g |
| Manufacturer designation | NTN 32311CU |
| Standard | ISO 355 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); 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 & 32300-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.791 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 32.5 mm |
| Smallest bore in 32300-series | 20 mm |
| Largest outer diameter in 32300-series | 460 mm |
| Width range across 32300-series | 22.25–154 mm |
| Bore position in 32300-series (smallest first) | 9 of 30 |
| Bore above smallest 32300-series size | 35 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 32311CU | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 32311CU model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, the NTN order number 32311CU denotes the extra-heavy 32300 family of metric tapered roller bearings, 55 mm bore, 120 mm outside diameter and 45.5 mm assembled width T (2.165 × 4.724 × 1.791 in) to the ISO 355 boundary plan. The last two digits 11 are the ISO bore code, ×5 = 55 mm (codes 00–03 use the 10/12/15/17 exception table) under the ISO 355 numbering; the 45.5 mm value printed here is T, the width of the fully assembled cone-plus-cup set, not the inner-ring width alone. The 32.5 mm radial section carries the roller complement across the 55–120 mm envelope; section and contact angle differ between NTN metric families even at the same bore, so 302/322/323 are not drop-in swaps. Selection: C 204 kN against C0 252 kN gives a C0/C ratio of 1.24 for the 55 mm bore, and the equivalent combined load must keep below the rating at the target L10 with the pair counted as one unit. Mount the 55 mm-bore cone on the shaft first (induction heat, max 120 °C), fit the cup square in its housing, then set preload or end play; never drive the cup home through the rollers of 32311CU.
Typical equipment & failure modes
Common applications
- industrial gearbox and speed-reducer shafts
- bevel and helical pinion drives with high thrust component
- pump and compressor drive shafts carrying combined load
- machine-tool gearbox and headstock shafts
Known failure patterns
- cone-raceway spalling at the large rib when preload is set too high for the lubricant film
- rib scoring when axial load is carried beyond the cone rib capacity of the adjusted pair
- preload loss from racewear when one bearing of the paired set is replaced without re-adjusting end play
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Hub and pinion bearings of this 55 mm bore class are commonly adjusted in pairs; verify end play against the axle drawing and re-torque after bedding-in rather than trusting the initial preload on 32311CU.
- The extra-heavy 32300 family at 55 mm bore (120×45.5 mm assembled) carries more capacity than the lighter 320/329 sections but generates more preload heat; confirm oil availability before running near the 4,200 r/min oil ceiling.
- Back-to-back and face-to-face arrangements react differently to shaft bending: pick the pair orientation for the moment load before locking the 55 mm shoulder geometry, because retrofitting flips the cups.
- ISO 355 makes the 55×120 mm envelope interchangeable but not the ratings: NTN prints 204/252 kN for this execution, and a cheaper same-number part can differ in roller complement and steel.
- The U/UTG/X/C/CA/D suffix variants of a base number share the bore but not the article: ordering 32311CU by size alone can deliver the wrong contact-angle execution for a pinion position.
- The 204/252 kN ratings and 30.5 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 32311CU (ISO 355 5FD); internal geometry legitimately differs between manufacturers, so re-verify ratings, adjustment and suffix before substituting another make on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 32311CU?
32311CU is a metric 4T tapered roller bearing to ISO 355: 55 mm bore, 120 mm outside diameter and 45.5 mm assembled width T (2.165 × 4.724 × 1.791 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 204 kN, C0 252 kN, Pu 30.5 kN, grease limiting speed 3,100 r/min, oil speed 4,200 r/min, mass about 2470 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 32311CU?
4T is NTN's tapered roller bearing brand mark, stamped on the cone and cup in the factory. It identifies the NTN 4T programme and is not a dimension, so the catalogue and this page list the bare ISO 355 number (32311CU); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 32311CU designation encode the 55 mm bore and what is 5FD?
last two digits 11 are the ISO bore code, ×5 = 55 mm (codes 00–03 use the 10/12/15/17 exception table). The 120 mm OD and 45.5 mm assembled T follow the ISO 355 dimension-series plan. 5FD is the maker-neutral ISO 355 abbreviation for this dimension series (the same code other manufacturers print); 4T is NTN's own brand mark.
Why does 32311CU list two speeds, 3,100 and 4,200 r/min?
The lower figure, 3,100 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 32311CU at 4,200 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 32311CU mean?
Suffix reading on 32311CU: U marks the reinforced/uprated internal design of the bare number, a separate order number with higher load capacity than the basic execution; the CA/CU/DU letter marks a contact-angle/internal-geometry variant of the same envelope — quote the exact suffix because axial/radial capacity split differs; the suffix is part of the order number and the variants are not interchangeable articles.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.