31326XU bearing: complete specifications & equivalents
The 31326XU is a ISO 355 radial bearing sized 130 x 280 x 72 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 130 mm |
| Outer diameter D | 280 mm |
| Width B | 72 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 670 kN |
| Basic static load rating C0 | 780 kN |
| Fatigue load limit Pu | 77 kN |
| Limiting speed (mechanical) | 1400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 19000 g |
| Manufacturer designation | NTN 31326XU |
| 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 & 31300-series range
| Bore d | 5.118 in |
|---|---|
| Outer diameter D | 11.024 in |
| Width B | 2.835 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 75 mm |
| Smallest bore in 31300-series | 25 mm |
| Largest outer diameter in 31300-series | 320 mm |
| Width range across 31300-series | 18.25–82 mm |
| Bore position in 31300-series (smallest first) | 20 of 22 |
| Bore above smallest 31300-series size | 105 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 31326XU | 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 31326XU model number is decoded
The NTN 2203E table prints 31326XU in the steep-angle 31300 family for high axial load share: 130 mm bore, 280 mm cup OD, 72 mm T, with a grease limiting speed of 1,400 r/min and an oil-lubricated ceiling of 1,800 r/min. Digit by digit, the bare number identifies the steep-angle 31300 family for high axial load share and a bore code resolving to 130 mm; 280 mm OD and 72 mm assembled T are the matching ISO 355 boundary dimensions shared with other makers of the same dimension series. Individually mounted, 31326XU takes axial force in one direction only; two bearings are arranged face-to-face (X) or back-to-back (O) according to the moment stiffness and misalignment the shaft requires. Catalogue mass of the 31326XU set is 19000 g (0.748 lb cone + cup); abutment and shaft shoulder design must carry that mass square to the axis. Open 4T bearings need application seals; without them the grease at the cone rib of 31326XU washes out and the rib/roller-end contact smears on the first wet or dusty shift.
Typical equipment & failure modes
Common applications
- offshore crane and drawworks drums
- heavy haul railway traction gearboxes
- large marine propulsion reduction gears
- cement-plant kiln and mill drive trains
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
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- false brinelling on a stationary paired set exposed to external vibration
Selection pitfalls — read before you substitute
- At 130 mm bore the 31326XU set is adjusted with hydraulic nuts on large mill and wind positions; follow the drive-up angle/end-play procedure, because manual torque methods cannot control preload at the 670 kN C level.
- The steeper contact angle of the steep-angle 31300 family for high axial load share raises axial capacity but lowers the speed ceiling against a 302/322 bearing at 130 mm bore; do not swap to the lighter family without re-checking the 1,400 r/min grease limit and the thrust load split.
- Do not confuse T (72 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.
- Do not confuse T (72 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.
- Never fit the 130 mm cone by hammering the 280 mm cup: force for both press fits goes through the ring faces only, or brinell marks release as noise within the first running hours.
- The 670/780 kN ratings and 77 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 31326XU (ISO 355 7GB); 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 31326XU?
31326XU is a metric 4T tapered roller bearing to ISO 355: 130 mm bore, 280 mm outside diameter and 72 mm assembled width T (5.118 × 11.024 × 2.835 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 670 kN, C0 780 kN, Pu 77 kN, grease limiting speed 1,400 r/min, oil speed 1,800 r/min, mass about 19000 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 31326XU?
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 (31326XU); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 31326XU designation encode the 130 mm bore and what is 7GB?
last two digits 26 are the ISO bore code, ×5 = 130 mm (codes 00–03 use the 10/12/15/17 exception table). The 280 mm OD and 72 mm assembled T follow the ISO 355 dimension-series plan. 7GB 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 31326XU list two speeds, 1,400 and 1,800 r/min?
The lower figure, 1,400 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 31326XU at 1,800 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 31326XU mean?
Suffix reading on 31326XU: XU combines the X ISO boundary section with the U uprated internal design; 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.