30313U bearing: complete specifications & equivalents
The 30313U is a ISO 355 radial bearing sized 65 x 140 x 36 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 65 mm |
| Outer diameter D | 140 mm |
| Width B | 36 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 225 kN |
| Basic static load rating C0 | 238 kN |
| Fatigue load limit Pu | 28.7 kN |
| Limiting speed (mechanical) | 2800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2540 g |
| Manufacturer designation | NTN 30313U |
| 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 | 2.559 in |
|---|---|
| Outer diameter D | 5.512 in |
| Width B | 1.417 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 37.5 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) | 12 of 32 |
| Bore above smallest 30300-series size | 50 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30313U | 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 30313U model number is decoded
30313U belongs to the NTN metric 4T tapered roller range (large-OD 30300 family with the steeper contact angle); the open bearing leaves sealing to the application and is normally ordered and mounted as an adjustable matched pair. Reading the designation: the leading five digits follow the ISO 355 metric plan (dimension family plus two-digit bore code), and 30313U resolves to 65 mm bore; the NTN factory mark 4T is stamped on cone and cup but is a brand mark, not a size code, so the catalogue sku is printed without it. The printed contact-angle geometry gives the large-OD 30300 family with the steeper contact angle its characteristic load split — at 225/238 kN (C/C0) the static rating is about 1.06× C, typical of tapered bearings proportioned for heavy combined duty. Selection: C 225 kN against C0 238 kN gives a C0/C ratio of 1.06 for the 65 mm bore, and the equivalent combined load must keep below the rating at the target L10 with the pair counted as one unit. Open 4T bearings need application seals; without them the grease at the cone rib of 30313U washes out and the rib/roller-end contact smears on the first wet or dusty shift.
Typical equipment & failure modes
Common applications
- rolling-mill auxiliary and pinion-stand shafts
- large conveyor and bucket-elevator pulleys
- mineral-processing feeder and crusher auxiliaries
- marine winch and deck-machinery 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
- cage fatigue when the pair is run continuously near the grease limiting speed without oil cooling
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Mount the 65 mm cone by induction heating (max 120 °C) and the cup with a press sleeve; the 2540 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 65 mm bore; do not swap to the lighter family without re-checking the 2,800 r/min grease limit and the thrust load split.
- Replacing one half of an adjusted pair without resetting end play negates the 36 mm T dimension logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- Open 30313U units have no seals: a wheel-hub or gearbox application needs external sealing or the 2,800 r/min grease figure is meaningless once water reaches the cone rib.
- Minimum load matters at high speed: an unloaded 30313U at a large fraction of 2,800 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded pair arrangements.
- The 225/238 kN ratings and 28.7 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30313U (ISO 355 2GB); 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 30313U?
30313U is a metric 4T tapered roller bearing to ISO 355: 65 mm bore, 140 mm outside diameter and 36 mm assembled width T (2.559 × 5.512 × 1.417 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 225 kN, C0 238 kN, Pu 28.7 kN, grease limiting speed 2,800 r/min, oil speed 3,700 r/min, mass about 2540 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30313U?
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 (30313U); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30313U designation encode the 65 mm bore and what is 2GB?
last two digits 13 are the ISO bore code, ×5 = 65 mm (codes 00–03 use the 10/12/15/17 exception table). The 140 mm OD and 36 mm assembled T follow the ISO 355 dimension-series plan. 2GB 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 30313U list two speeds, 2,800 and 3,700 r/min?
The lower figure, 2,800 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30313U at 3,700 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30313U mean?
Suffix reading on 30313U: 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.