32309U bearing: complete specifications & equivalents
The 32309U 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 | 170 kN |
| Basic static load rating C0 | 191 kN |
| Fatigue load limit Pu | 23.3 kN |
| Limiting speed (mechanical) | 4000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1450 g |
| Manufacturer designation | NTN 32309U |
| 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 |
|---|---|---|---|
| 32309U | 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 32309U model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, the NTN order number 32309U denotes the extra-heavy 32300 family of metric tapered roller bearings, 45 mm bore, 100 mm outside diameter and 38.25 mm assembled width T (1.772 × 3.937 × 1.506 in) to the ISO 355 boundary plan. 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. Suffix reading on 32309U: U marks the reinforced/uprated internal design of the bare number, a separate order number with higher load capacity than the basic execution; the suffix is part of the order number and the variants are not interchangeable articles. Selection: C 170 kN against C0 191 kN gives a C0/C ratio of 1.12 for the 45 mm bore, and the equivalent combined load must keep below the rating at the target L10 with the pair counted as one unit. Re-adjustment after bedding-in is standard practice: re-check end play once the paired 32309U arrangement has run in, because initial seat seating relaxes the set preload slightly.
Typical equipment & failure modes
Common applications
- axle final-drive and differential positions
- construction-equipment wheel and pivot hubs
- truck and bus wheel hubs in paired arrangements
- industrial gearbox and speed-reducer shafts
Known failure patterns
- cup creep and housing fretting when the specified outer-ring press fit is not achieved
- preload loss from racewear when one bearing of the paired set is replaced without re-adjusting end play
- rib scoring when axial load is carried beyond the cone rib capacity of the adjusted pair
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- water-induced pitting when the open bearing is exposed to washdown without external seals
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 32309U.
- 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 5,300 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 45 mm shoulder geometry, because retrofitting flips the cups.
- Never fit the 45 mm cone by hammering the 100 mm cup: force for both press fits goes through the ring faces only, or brinell marks release as noise within the first running hours.
- ISO 355 makes the 45×100 mm envelope interchangeable but not the ratings: NTN prints 170/191 kN for this execution, and a cheaper same-number part can differ in roller complement and steel.
- The 170/191 kN ratings and 23.3 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 32309U (ISO 355 2FD); 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 32309U?
32309U 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 170 kN, C0 191 kN, Pu 23.3 kN, grease limiting speed 4,000 r/min, oil speed 5,300 r/min, mass about 1450 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 32309U?
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 (32309U); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 32309U designation encode the 45 mm bore and what is 2FD?
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. 2FD 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 32309U list two speeds, 4,000 and 5,300 r/min?
The lower figure, 4,000 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 32309U at 5,300 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 32309U mean?
Suffix reading on 32309U: U marks the reinforced/uprated internal design of the bare number, a separate order number with higher load capacity than the basic execution; 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.