30203-NTN bearing: complete specifications & equivalents
The 30203-NTN is a ISO 355 radial bearing sized 17 x 40 x 13.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 17 mm |
| Outer diameter D | 40 mm |
| Width B | 13.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 22.7 kN |
| Basic static load rating C0 | 20.3 kN |
| Limiting speed (mechanical) | 9900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 80 g |
| Manufacturer designation | NTN 30203 |
| 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 & 30200-series range
| Bore d | 0.669 in |
|---|---|
| Outer diameter D | 1.575 in |
| Width B | 0.522 in |
| ISO bore code | 03 |
| Radial section height (D−d)/2 | 11.5 mm |
| Smallest bore in 30200-series | 15 mm |
| Largest outer diameter in 30200-series | 580 mm |
| Width range across 30200-series | 11.75–104 mm |
| Bore position in 30200-series (smallest first) | 2 of 37 |
| Bore above smallest 30200-series size | 2 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30203 | SKF | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
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 30203-NTN model number is decoded
30203 is the NTN 4T catalogue entry for a 17×40×13.25 mm metric tapered roller bearing — separable cone and cup, designed for combined radial and axial load as an individually adjusted bearing. On the NTN nameplate the parts carry 4T plus the bare code, while 2203E orders 30203 by the metric ISO 355 number (ISO series abbreviation 2DB): 17 mm bore, 40 mm OD. NTN adjusts these bearings by cup or cone position rather than shipping a preloaded set; the mounting drawing must state end play or preload for 30203, since running clearance is set during assembly. The 1.3 kN-per-mm-bore capacity figure for 30203 summarises the 22.7 kN rating over 17 mm bore; use it to sanity-check an interchange candidate before swapping brands. Fillet radii must clear the ring chamfers of the 40 mm cup and 17 mm cone; use undercut shoulders so the rings seat fully rather than bridging on a shaft radius.
Typical equipment & failure modes
Common applications
- scooter and light-powersport wheel and gear positions
- small conveyor pulley shafts
- steering-knuckle and kingpin positions
- small automotive wheel hubs and trailer axles
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
- cage fatigue when the pair is run continuously near the grease limiting speed without oil cooling
- false brinelling on a stationary paired set exposed to external vibration
Selection pitfalls — read before you substitute
- At 17 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 30203 pair with a dial indicator rather than by feel.
- The standard-section 30200 family at 17 mm bore (40×13.25 mm assembled) carries more capacity than the lighter 320/329 sections but generates more preload heat; confirm oil availability before running near the 13,000 r/min oil ceiling.
- Minimum load matters at high speed: an unloaded 30203 at a large fraction of 9,900 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded pair arrangements.
- Back-to-back and face-to-face arrangements react differently to shaft bending: pick the pair orientation for the moment load before locking the 17 mm shoulder geometry, because retrofitting flips the cups.
- On slash-size and T-code bearings confirm the full code on both cone and cup before fitting: the 17 mm bore alone does not identify the cup, and a mismatched cone/cup set has no catalogue rating.
- The 22.7/20.3 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30203 (ISO 355 2DB); 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 30203?
30203 is a metric 4T tapered roller bearing to ISO 355: 17 mm bore, 40 mm outside diameter and 13.25 mm assembled width T (0.669 × 1.575 × 0.522 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 22.7 kN, C0 20.3 kN (2203E prints no Pu for this size), grease limiting speed 9,900 r/min, oil speed 13,000 r/min, mass about 80 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30203?
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 (30203); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30203 designation encode the 17 mm bore and what is 2DB?
last two digits 03 are the ISO bore code, ×5 = 17 mm (codes 00–03 use the 10/12/15/17 exception table). The 40 mm OD and 13.25 mm assembled T follow the ISO 355 dimension-series plan. 2DB 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 30203 list two speeds, 9,900 and 13,000 r/min?
The lower figure, 9,900 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30203 at 13,000 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30203 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.