30305-NTN bearing: complete specifications & equivalents
The 30305-NTN is a ISO 355 radial bearing sized 25 x 62 x 18.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 25 mm |
| Outer diameter D | 62 mm |
| Width B | 18.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 54 kN |
| Basic static load rating C0 | 47.5 kN |
| Limiting speed (mechanical) | 6700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 268 g |
| Manufacturer designation | NTN 30305 |
| 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 | 0.984 in |
|---|---|
| Outer diameter D | 2.441 in |
| Width B | 0.719 in |
| ISO bore code | 05 |
| Radial section height (D−d)/2 | 18.5 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) | 4 of 32 |
| Bore above smallest 30300-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30305 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 25×62×18.25 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
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 30305-NTN model number is decoded
The NTN 2203E table prints 30305 in the large-OD 30300 family with the steeper contact angle: 25 mm bore, 62 mm cup OD, 18.25 mm T, with a grease limiting speed of 6,700 r/min and an oil-lubricated ceiling of 8,900 r/min. Digit by digit, the bare number identifies the large-OD 30300 family with the steeper contact angle and a bore code resolving to 25 mm; 62 mm OD and 18.25 mm assembled T are the matching ISO 355 boundary dimensions shared with other makers of the same dimension series. NTN grades 4T metric bearings as open bearings without integral seals; at 25 mm bore the application supplies the seals and the grease fill or oil supply to the 2FB ISO 355 assembly. The 2.2 kN-per-mm-bore capacity figure for 30305 summarises the 54 kN rating over 25 mm bore; use it to sanity-check an interchange candidate before swapping brands. Mount the 25 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 30305.
Typical equipment & failure modes
Common applications
- light-vehicle differential and pinion shafts
- agricultural implement hubs and ground-tool drives
- small gearbox input shafts with combined load
- scooter and light-powersport wheel and gear positions
Known failure patterns
- cup creep and housing fretting when the specified outer-ring press fit is not achieved
- smearing on the roller large ends and cone rib after a dry start with preload but no oil film
- flaking on one cone only when a back-to-back / face-to-face pair is loaded unevenly by a bent shaft
- cage damage from a mounting blow delivered through the roller complement instead of the ring face
- edge loading when shaft deflection exceeds the few arc-minutes of misalignment the adjusted pair allows
Selection pitfalls — read before you substitute
- At 25 mm bore the thin section and small rollers are adjustment-sensitive: a quarter-turn of the locknut moves end play by more than on large bearings, so set the 30305 pair with a dial indicator rather than by feel.
- 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 25 mm bore; do not swap to the lighter family without re-checking the 6,700 r/min grease limit and the thrust load split.
- Replacing one half of an adjusted pair without resetting end play negates the 18.25 mm T dimension logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- Never fit the 25 mm cone by hammering the 62 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 18.5 mm section leaves little room for an oversized shaft fillet; check the mounting-chamfer table for 30305 or the ring will bottom out on the radius instead of the shoulder face.
- The 54/47.5 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30305 (ISO 355 2FB); 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 30305?
30305 is a metric 4T tapered roller bearing to ISO 355: 25 mm bore, 62 mm outside diameter and 18.25 mm assembled width T (0.984 × 2.441 × 0.719 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 54 kN, C0 47.5 kN (2203E prints no Pu for this size), grease limiting speed 6,700 r/min, oil speed 8,900 r/min, mass about 268 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30305?
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 (30305); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30305 designation encode the 25 mm bore and what is 2FB?
last two digits 05 are the ISO bore code, ×5 = 25 mm (codes 00–03 use the 10/12/15/17 exception table). The 62 mm OD and 18.25 mm assembled T follow the ISO 355 dimension-series plan. 2FB 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 30305 list two speeds, 6,700 and 8,900 r/min?
The lower figure, 6,700 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30305 at 8,900 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30305 mean?
It is the basic open 4T execution — steel cage, adjusted mounting, no seal or feature suffix. NTN uses U for the uprated design, UTG for ULTAGE large-bearing specs, X for the ISO boundary section, and C/CA/D/A for contact-angle or internal-design variants; all are separate order numbers.
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.