2878-2820 bearing: complete specifications & equivalents
The 2878-2820 is a ANSI ABMA 19.2 radial bearing sized 34.925 x 73.025 x 22.225 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 34.925 mm |
| Outer diameter D | 73.025 mm |
| Width B | 22.225 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 69.5 kN |
| Basic static load rating C0 | 75.5 kN |
| Limiting speed (mechanical) | 5200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 435 g |
| Manufacturer designation | NTN 4T-2878/2820 |
| Standard | ANSI ABMA 19.2 |
| Catalog version | NTN 2203E 2026-09-25 |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN 2203E 2026-09-25) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN 2203E 2026-09-25); 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 & 4t-inch-series range
| Bore d | 1.375 in |
|---|---|
| Outer diameter D | 2.875 in |
| Width B | 0.875 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 19.1 mm |
| Smallest bore in 4t-inch-series | 12.7 mm |
| Largest outer diameter in 4t-inch-series | 260 mm |
| Width range across 4t-inch-series | 10.998–77.788 mm |
| Bore position in 4t-inch-series (smallest first) | 34 of 148 |
| Bore above smallest 4t-inch-series size | 22.224999999999998 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 2878 | 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 2878-2820 model number is decoded
The NTN 2203E inch table prints 4T-2878/2820 at 34.925 mm bore (1.375 in), 73.025 mm cup OD and 22.225 mm assembled T, with a grease limiting speed of 5,200 r/min and an oil ceiling of 7,000 r/min. Unlike ISO 355 metric numbers, this ABMA code does not encode the bore arithmetically: 2878 identifies the cone of 34.925 mm (1.375 in) bore by catalogue lookup, and 2820 fixes the 73.025 mm OD. Grease relubrication at the 5,200 r/min limiting speed targets the cone-rib contact; sustaining 7,000 r/min needs an oil supply directed at the large roller ends. The printed 69.5/75.5 kN ratings belong to the assembled 2878+2820 pair; a sibling row using the same cone with a different cup carries its own rating row because the raceway track shifts with the cup. The rollers run with their large ends against the cone's guide rib; lubricant must reach that rib face of 4T-2878/2820, not only the raceway, or the pair smears on the first overloaded start.
Typical equipment & failure modes
Common applications
- truck and trailer axle hubs on inch-dimensioned axles
- agricultural tractor transmission and PTO shafts
- industrial gearboxes built to inch shafting
- construction-equipment pivot and wheel positions
Known failure patterns
- rib-face scoring when the thrust share of the combined load exceeds what the cone rib of this size carries
- preload loss and noise after one bearing of the adjusted pair is replaced without resetting end play
- false brinelling on a stationary pair exposed to vibration during transport or standby
- cage fatigue when the pair runs continuously near the grease limiting speed without oil cooling
- water-induced pitting when the open bearing sees washdown without external seals
Selection pitfalls — read before you substitute
- Hub and pinion positions of this 34.925 mm class are adjusted in pairs; verify end play against the axle or gearbox drawing and re-torque after bedding-in instead of trusting the first setting on 4T-2878/2820.
- The pure-numeric inch family at 34.925 mm bore (73.025×22.225 mm assembled) is one of several inch families sharing similar bores; cross-series swaps change OD, T and contact angle, so match the full 2878/2820 reference at purchase.
- Shaft and housing fillets must clear the ring chamfers of 2878 and 2820; use undercut shoulders so the rings seat on the face, not on a radius.
- Shaft and housing fillets must clear the ring chamfers of 2878 and 2820; use undercut shoulders so the rings seat on the face, not on a radius.
- Quote the full 2878/2820 pair at ordering: the 2878 cone also ships against sibling cups, and a cup from another reference changes the 22.225 mm assembled width and the rating.
- The 69.5/75.5 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 4T-2878/2820; internal geometry legitimately differs between inch-series makers, so re-verify ratings, adjustment and the exact cone/cup references before substituting another brand on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 4T-2878/2820?
4T-2878/2820 is an inch-series single-row tapered roller bearing to the ABMA boundary plan: 34.925 mm bore (1.375 in), 73.025 mm outside diameter and 22.225 mm assembled width T (2.875 × 0.875 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 69.5 kN, C0 75.5 kN, grease limiting speed 5,200 r/min, oil speed 7,000 r/min, mass about 435 g. It is an open, separable cone/cup set with a pressed-steel cage.
Are the cone and cup of 4T-2878/2820 interchangeable separately?
Yes — ABMA inch parts are individually interchangeable: the 2878 cone or the 2820 cup can be replaced by an identical reference from NTN or another ABMA-dimensioned maker. Pairing the cone with a different cup reference is a different catalogue row: OD, assembled T and the 69.5/75.5 kN ratings change with the cup.
What is the difference between 4T-2878/2820 and a metric ISO 355 tapered bearing?
4T-2878/2820 follows the ABMA inch boundary plan with cone/cup references; ISO 355 bearings use metric dimension-series numbers (302, 322, …). Even where a metric size looks close to 34.925×73.025×22.225 mm, the envelopes and contact angles differ — the two systems are not drop-in interchangeable; check every boundary value before substituting.
What does the 4T prefix on 4T-2878/2820 mean?
4T is NTN's tapered roller bearing quality mark, stamped on cone and cup in the factory. It identifies NTN's 4T programme and is not a dimension or variant code, so interchange lists quote the bare 2878/2820 references; the 4T spelling is retained among this page's search aliases.
Why does 4T-2878/2820 list two speeds, 5,200 and 7,000 r/min?
The lower figure, 5,200 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 4T-2878/2820 at 7,000 r/min because oil removes rib-contact heat better. Real limits still depend on pair adjustment, oil flow and cooling.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN 2203E 2026-09-25 on 2026-10-01. Read our editorial & correction policy.