30304CA bearing: complete specifications & equivalents
The 30304CA is a ISO 355 radial bearing sized 20 x 52 x 16.25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 20 mm |
| Outer diameter D | 52 mm |
| Width B | 16.25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 34.5 kN |
| Basic static load rating C0 | 31 kN |
| Limiting speed (mechanical) | 7600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 170 g |
| Manufacturer designation | NTN 30304CA |
| 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 | 0.787 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.64 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 16 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) | 3 of 32 |
| Bore above smallest 30300-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30304CA | 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 30304CA model number is decoded
For a 20 mm shaft with a thrust component, NTN lists 30304CA, a metric 4T tapered roller bearing of 34.5 kN C and 31 kN C0 inside the 52 mm OD, 16.25 mm-wide assembled set. Digit by digit, the bare number identifies the large-OD 30300 family with the steeper contact angle and a bore code resolving to 20 mm; 52 mm OD and 16.25 mm assembled T are the matching ISO 355 boundary dimensions shared with other makers of the same dimension series. A tapered roller bearing reacts combined radial and one-direction axial load; NTN mounts 30304CA cone and cup separately and adjusts end play or preload against a second bearing, so the arrangement locates the shaft in both directions. Catalogue mass of the 30304CA set is 170 g (0.007 lb cone + cup); abutment and shaft shoulder design must carry that mass square to the axis. When pairing 30304CA with a second tapered bearing, keep the matched arrangement clean: a single stray grit particle between cup and housing changes preload faster than the adjustment range can correct.
Typical equipment & failure modes
Common applications
- small automotive wheel hubs and trailer axles
- light-vehicle differential and pinion shafts
- agricultural implement hubs and ground-tool drives
- small gearbox input shafts with combined load
Known failure patterns
- cone-raceway spalling at the large rib when preload is set too high for the lubricant film
- 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
- rolling-contact fatigue after the catalogue L10 life at the actual combined load
Selection pitfalls — read before you substitute
- At 20 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 30304CA 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 20 mm bore; do not swap to the lighter family without re-checking the 7,600 r/min grease limit and the thrust load split.
- Do not confuse T (16.25 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.
- Open 30304CA units have no seals: a wheel-hub or gearbox application needs external sealing or the 7,600 r/min grease figure is meaningless once water reaches the cone rib.
- Do not confuse T (16.25 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.
- The 34.5/31 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30304CA; 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 30304CA?
30304CA is a metric 4T tapered roller bearing to ISO 355: 20 mm bore, 52 mm outside diameter and 16.25 mm assembled width T (0.787 × 2.047 × 0.64 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 34.5 kN, C0 31 kN (2203E prints no Pu for this size), grease limiting speed 7,600 r/min, oil speed 10,000 r/min, mass about 170 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30304CA?
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 (30304CA); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30304CA designation encode the 20 mm bore?
last two digits 04 are the ISO bore code, ×5 = 20 mm (codes 00–03 use the 10/12/15/17 exception table). The 52 mm OD and 16.25 mm assembled T follow the ISO 355 dimension-series plan.
Why does 30304CA list two speeds, 7,600 and 10,000 r/min?
The lower figure, 7,600 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30304CA at 10,000 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30304CA mean?
Suffix reading on 30304CA: 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.