30318DU bearing: complete specifications & equivalents
The 30318DU is a ISO 355 radial bearing sized 90 x 190 x 46.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 90 mm |
| Outer diameter D | 190 mm |
| Width B | 46.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 300 kN |
| Basic static load rating C0 | 320 kN |
| Fatigue load limit Pu | 35.5 kN |
| Limiting speed (mechanical) | 1800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 5580 g |
| Manufacturer designation | NTN 30318DU |
| 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 & 30300-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.831 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 50 mm |
| Smallest bore in 30300-series | 15 mm |
| Largest outer diameter in 30300-series | 500 mm |
| Width range across 30300-series | 14.25–105 mm |
| Bore position in 30300-series (smallest first) | 17 of 32 |
| Bore above smallest 30300-series size | 75 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30318DU | 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 30318DU model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, the NTN order number 30318DU denotes the large-OD 30300 family with the steeper contact angle of metric tapered roller bearings, 90 mm bore, 190 mm outside diameter and 46.5 mm assembled width T (3.543 × 7.48 × 1.831 in) to the ISO 355 boundary plan. NTN also quotes this bearing with its ISO 355 dimension-series abbreviation, 7GB, which is the maker-neutral cross-reference for the 90×190 mm envelope; 4T is NTN's own tapered-roller brand mark on the parts. 2203E lists two speed ceilings for 30318DU: 1,800 r/min with grease lubrication (the limiting speed) and 2,400 r/min with oil, the higher oil value reflecting better heat removal from the cone rib. Grease relubrication at 1,800 r/min limiting speed targets the rib contact; if the drive needs 2,400 r/min it must be arranged for oil lubrication with a defined flow to the large roller ends. Mount the 90 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 30318DU.
Typical equipment & failure modes
Common applications
- paper-machine press-section rolls
- large agricultural and forestry machine axles
- heavy industrial gearboxes and crane travel drives
- rolling-mill auxiliary and pinion-stand shafts
Known failure patterns
- cup creep and housing fretting when the specified outer-ring press fit is not achieved
- 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
- cage damage from a mounting blow delivered through the roller complement instead of the ring face
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Mount the 90 mm cone by induction heating (max 120 °C) and the cup with a press sleeve; the 5580 g ring mass makes cocking during fitting a direct raceway-brinelling risk.
- The steeper contact angle of the large-OD 30300 family with the steeper contact angle raises axial capacity but lowers the speed ceiling against a 302/322 bearing at 90 mm bore; do not swap to the lighter family without re-checking the 1,800 r/min grease limit and the thrust load split.
- Never fit the 90 mm cone by hammering the 190 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 90×190 mm envelope interchangeable but not the ratings: NTN prints 300/320 kN for this execution, and a cheaper same-number part can differ in roller complement and steel.
- Grease packs must leave free volume in the 46.5 mm-wide set; over-greasing a paired bearing churning at the 2,400 r/min oil-band speed raises temperature and destroys the preload setting.
- The 300/320 kN ratings and 35.5 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30318DU (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 30318DU?
30318DU is a metric 4T tapered roller bearing to ISO 355: 90 mm bore, 190 mm outside diameter and 46.5 mm assembled width T (3.543 × 7.48 × 1.831 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 300 kN, C0 320 kN, Pu 35.5 kN, grease limiting speed 1,800 r/min, oil speed 2,400 r/min, mass about 5580 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30318DU?
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 (30318DU); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30318DU designation encode the 90 mm bore and what is 7GB?
last two digits 18 are the ISO bore code, ×5 = 90 mm (codes 00–03 use the 10/12/15/17 exception table). The 190 mm OD and 46.5 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 30318DU list two speeds, 1,800 and 2,400 r/min?
The lower figure, 1,800 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30318DU at 2,400 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30318DU mean?
Suffix reading on 30318DU: 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.