32309CU bearing: complete specifications & equivalents
The 32309CU is a ISO 355 radial bearing sized 45 x 100 x 38.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 45 mm |
| Outer diameter D | 100 mm |
| Width B | 38.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 145 kN |
| Basic static load rating C0 | 175 kN |
| Fatigue load limit Pu | 21.4 kN |
| Limiting speed (mechanical) | 3800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1470 g |
| Manufacturer designation | NTN 32309CU |
| 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 | 1.772 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 1.506 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 27.5 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) | 7 of 30 |
| Bore above smallest 32300-series size | 25 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 32309CU | 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 32309CU model number is decoded
32309CU is a metric single-row tapered roller bearing in the NTN 4T programme: a pressed-steel cage guides profiled rollers between a separable cone and cup on the 45×100 mm ISO 355 envelope, with 38.25 mm overall assembled width T. The last two digits 09 are the ISO bore code, ×5 = 45 mm (codes 00–03 use the 10/12/15/17 exception table) under the ISO 355 numbering; the 38.25 mm value printed here is T, the width of the fully assembled cone-plus-cup set, not the inner-ring width alone. A tapered roller bearing reacts combined radial and one-direction axial load; NTN mounts 32309CU cone and cup separately and adjusts end play or preload against a second bearing, so the arrangement locates the shaft in both directions. The 27.5 mm section height over the 45 mm bore positions the load centre; axial location of the pair depends on that contact line, so spacer faces must be square within the P0 tolerance of the bearing. With a rotating shaft a k5/m5 shaft seat and a press-fit cup are typical catalogue practice for 32309CU; reverse the logic if the cup rotates, and re-verify against load direction and magnitude.
Typical equipment & failure modes
Common applications
- bevel and helical pinion drives with high thrust component
- pump and compressor drive shafts carrying combined load
- machine-tool gearbox and headstock shafts
- axle final-drive and differential positions
Known failure patterns
- cup creep and housing fretting when the specified outer-ring press fit is not achieved
- flaking on one cone only when a back-to-back / face-to-face pair is loaded unevenly by a bent shaft
- smearing on the roller large ends and cone rib after a dry start with preload but no oil film
- cage damage from a mounting blow delivered through the roller complement instead of the ring face
- false brinelling on a stationary paired set exposed to external vibration
Selection pitfalls — read before you substitute
- Hub and pinion bearings of this 45 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 32309CU.
- The extra-heavy 32300 family at 45 mm bore (100×38.25 mm assembled) carries more capacity than the lighter 320/329 sections but generates more preload heat; confirm oil availability before running near the 5,100 r/min oil ceiling.
- Grease packs must leave free volume in the 38.25 mm-wide set; over-greasing a paired bearing churning at the 5,100 r/min oil-band speed raises temperature and destroys the preload setting.
- The 27.5 mm section leaves little room for an oversized shaft fillet; check the mounting-chamfer table for 32309CU or the ring will bottom out on the radius instead of the shoulder face.
- Do not confuse T (38.25 mm assembled width of cone + cup) with the cone width when drawing spacers; an abutment sized to T instead of the ring width leaves the cup unseated.
- The 145/175 kN ratings and 21.4 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 32309CU (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 32309CU?
32309CU is a metric 4T tapered roller bearing to ISO 355: 45 mm bore, 100 mm outside diameter and 38.25 mm assembled width T (1.772 × 3.937 × 1.506 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 145 kN, C0 175 kN, Pu 21.4 kN, grease limiting speed 3,800 r/min, oil speed 5,100 r/min, mass about 1470 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 32309CU?
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 (32309CU); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 32309CU designation encode the 45 mm bore and what is 5FD?
last two digits 09 are the ISO bore code, ×5 = 45 mm (codes 00–03 use the 10/12/15/17 exception table). The 100 mm OD and 38.25 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 32309CU list two speeds, 3,800 and 5,100 r/min?
The lower figure, 3,800 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 32309CU at 5,100 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 32309CU mean?
Suffix reading on 32309CU: 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.