30308T72-DB bearing: complete specifications & equivalents
The 30308T72-DB is a ISO 355 radial bearing sized 40 x 90 x 72 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 72 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 182 kN |
| Basic static load rating C0 | 190 kN |
| Fatigue load limit Pu | 21.6 kN |
| Reference speed (thermal) | 5300 rpm |
| Limiting speed (mechanical) | 8000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1900 g |
| Manufacturer designation | SKF 30308T72/DB |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants |
| Last verified | 2026-09-29 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants) · extracted 2026-09-29
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & matched-db-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 2.835 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in matched-db-series | 35 mm |
| Largest outer diameter in matched-db-series | 480 mm |
| Width range across matched-db-series | 41.5–288 mm |
| Bore position in matched-db-series (smallest first) | 2 of 30 |
| Bore above smallest matched-db-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30308T72 | 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 30308T72-DB model number is decoded
The rotating cones of 30308T72-DB take a k5 seat on the 40 mm shaft; the cups are a transition-to-loose fit so the pair can be clamped to its factory setting during assembly.Ordering number SKF 30308T72/DB in SKF catalogue PUB BU/P1 17000 denotes two single-row tapered roller bearings supplied as a matched back-to-back (O) matched pair set for a 40 mm shaft — one order number, one factory setting.The code breaks down as base bearing 30308T72 plus matched-set suffix /DB: two bearings of the 40 mm bore size, paired back-to-back (O) matched pair, with the 72 mm overall width spanning the whole arrangement. Back-to-back matching puts the large rib ends outward — the stiffest arrangement for moment load, but one that converts shaft thermal growth into preload change; the factory setting of 30308T72-DB already accounts for the expected temperature gradient across the 72 mm pair width. Selection arithmetic: the catalogue C 182 kN and C0 190 kN are ratings of the complete pair, not of one bearing — never halve them back to a single-row figure when checking L10 life, and use the pair Pu 21.6 kN as the fatigue floor. Load system: C 182 kN against C0 190 kN gives a 1.04 balance, and 4.55 kN of dynamic capacity per millimetre of the 40 mm bore is the density figure to compare against neighbouring sizes. Inspection shorthand: at overhaul, mark both bearings and the spacer of 30308T72-DB before disassembly — the set is a matched system, and re-assembling with one component reversed changes the factory setting.
Typical equipment & failure modes
Common applications
- axle-boxes in material-handling equipment
- automotive and light-truck wheel hubs
- industrial gearbox shafts and reducers
- machine-tool spindles
Known failure patterns
- false brinelling on idle paired sets exposed to machine vibration
- preload loss as the mounted pair relaxes, letting rollers skid and smear the raceways
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- brinelling from pressing the cone or cup home through the rollers
- hard-particle indentation of the tapered raceway in unfiltered oil
Selection pitfalls — read before you substitute
- O and X arrangements are not interchangeable by turning the set around: 30308T72-DB in back-to-back (O) matched pair arrangement has its load-line geometry fixed — specify the arrangement from the shaft thermal and stiffness analysis.
- Spacer faces must stay parallel within the set's own tolerance; a tilted spacer in 30308T72-DB concentrates reversing thrust on one bearing and shows up as one-sided raceway wear.
- Clamp the 30308T72-DB pair axially through the cones, never through the rollers; pressing force across the roller complement brinells the raceways of both bearings at once.
- The 182/190 kN ratings are SKF catalogue 17000 values for this execution; SKF can revise internal geometry without changing the order number, so keep the catalogue version (PUB BU/P1 17000/1 EN, 2018) with the specification.
- Quote the full SKF 30308T72/DB designation when purchasing — base-number-only orders are ambiguous across executions and variants.
Frequently asked questions
What are the dimensions and catalogue data of 30308T72-DB?
The SKF 30308T72/DB is a matched pair of single-row tapered roller bearings in back-to-back (O) matched pair arrangement with 40 mm bore, 90 mm outer diameter and 72 mm overall width (1.575 × 3.543 × 2.835 in). From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 182 kN, C0 190 kN, fatigue load limit Pu 21.6 kN, reference speed 5,300 r/min, limiting speed 8,000 r/min, mass about 1.90 kg.
What does the /DB suffix on 30308T72-DB mean?
The base 30308T72 is the ISO 355 single-row bearing; the /DB suffix marks the matched-set execution — the arrangement (back-to-back (O)), the ground spacer and the factory-set axial clearance class. A matched set cannot be assembled from loose single bearings; quote the full designation when ordering.
Are the C and C0 ratings of 30308T72-DB for one bearing or the pair?
They are for the complete matched pair: C 182 kN dynamic and C0 190 kN static already include load sharing between the two bearings. Do not halve them for single-bearing checks, and do not compare them directly with the single-row 30308T72 table values.
Can 30308T72-DB be adjusted like two loose tapered bearings?
No — the axial clearance is set at the factory by selective spacer grinding. Mounting work is limited to clean seats, correct fits (k5 on a rotating 40 mm shaft) and axial clamping through the cones; re-setting in the field destroys the matched clearance class.
When should a back-to-back (O) matched set be chosen?
Choose the back-to-back (O) set where moment stiffness dominates — pinion supports, gearbox output shafts, crane sheaves. The diverging load lines give the widest effective spread at the 40 mm bore.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.3-8.8 TRB variants on 2026-09-29. Read our editorial & correction policy.