30306CA bearing: complete specifications & equivalents
The 30306CA is a ISO 355 radial bearing sized 30 x 72 x 20.75 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 30 mm |
| Outer diameter D | 72 mm |
| Width B | 20.75 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 65 kN |
| Basic static load rating C0 | 58.5 kN |
| Limiting speed (mechanical) | 5500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 399 g |
| Manufacturer designation | NTN 30306CA |
| 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 | 1.181 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 0.817 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 21 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) | 5 of 32 |
| Bore above smallest 30300-series size | 15 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30306CA | 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 30306CA model number is decoded
The NTN 2203E table prints 30306CA in the large-OD 30300 family with the steeper contact angle: 30 mm bore, 72 mm cup OD, 20.75 mm T, with a grease limiting speed of 5,500 r/min and an oil-lubricated ceiling of 7,300 r/min. The last two digits 06 are the ISO bore code, ×5 = 30 mm (codes 00–03 use the 10/12/15/17 exception table) under the ISO 355 numbering; the 20.75 mm value printed here is T, the width of the fully assembled cone-plus-cup set, not the inner-ring width alone. The pressed-steel cage and surface-finished roller ends are standard 4T execution; ULTAGE-marked variants use upgraded material and internal geometry aimed at longer rating life with the same ISO 355 envelope. Speed planning uses both catalogue columns: grease 5,500 r/min is the cage/rib mechanical ceiling for 30306CA, oil 7,300 r/min is available with circulating oil — a 1,800 r/min margin at this size. Open 4T bearings need application seals; without them the grease at the cone rib of 30306CA washes out and the rib/roller-end contact smears on the first wet or dusty shift.
Typical equipment & failure modes
Common applications
- machine-tool gearbox and headstock shafts
- axle final-drive and differential positions
- construction-equipment wheel and pivot hubs
- truck and bus wheel hubs in paired arrangements
Known failure patterns
- cone-raceway spalling at the large rib when preload is set too high for the lubricant film
- flaking on one cone only when a back-to-back / face-to-face pair is loaded unevenly by a bent shaft
- smearing on the roller large ends and cone rib after a dry start with preload but no oil film
- 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
- Hub and pinion bearings of this 30 mm bore class are commonly adjusted in pairs; verify end play against the axle drawing and re-torque after bedding-in rather than trusting the initial preload on 30306CA.
- 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 30 mm bore; do not swap to the lighter family without re-checking the 5,500 r/min grease limit and the thrust load split.
- Open 30306CA units have no seals: a wheel-hub or gearbox application needs external sealing or the 5,500 r/min grease figure is meaningless once water reaches the cone rib.
- Back-to-back and face-to-face arrangements react differently to shaft bending: pick the pair orientation for the moment load before locking the 30 mm shoulder geometry, because retrofitting flips the cups.
- Replacing one half of an adjusted pair without resetting end play negates the 20.75 mm T dimension logic: re-adjust the set and re-verify the contact pattern rather than reusing the old spacer stack.
- The 65/58.5 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 30306CA; 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 30306CA?
30306CA is a metric 4T tapered roller bearing to ISO 355: 30 mm bore, 72 mm outside diameter and 20.75 mm assembled width T (1.181 × 2.835 × 0.817 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 65 kN, C0 58.5 kN (2203E prints no Pu for this size), grease limiting speed 5,500 r/min, oil speed 7,300 r/min, mass about 399 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 30306CA?
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 (30306CA); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 30306CA designation encode the 30 mm bore?
last two digits 06 are the ISO bore code, ×5 = 30 mm (codes 00–03 use the 10/12/15/17 exception table). The 72 mm OD and 20.75 mm assembled T follow the ISO 355 dimension-series plan.
Why does 30306CA list two speeds, 5,500 and 7,300 r/min?
The lower figure, 5,500 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 30306CA at 7,300 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 30306CA mean?
Suffix reading on 30306CA: 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.