30311 bearing: complete specifications & equivalents
The 30311 is a ISO 355 radial bearing sized 55 x 120 x 31.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 31.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 176 kN |
| Basic static load rating C0 | 163 kN |
| Fatigue load limit Pu | 19.3 kN |
| Reference speed (thermal) | 4800 rpm |
| Limiting speed (mechanical) | 5600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1550 g |
| Manufacturer designation | SKF 30311 |
| Standard | ISO 355 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB |
| Last verified | 2026-09-26 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB) · extracted 2026-09-26
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB); 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 & 30300-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.24 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 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) | 10 of 32 |
| Bore above smallest 30300-series size | 40 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30311 | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 355 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
| 30311-NTN | NTN | 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 30311 model number is decoded
Ordering number SKF 30311 in SKF catalogue PUB BU/P1 17000 denotes a single-row tapered roller bearing for a 55 mm shaft, heavy-OD section, with an open pressed-steel-cage execution and one-direction axial capacity.Digit by digit, 30311 reads as bearing type 3 (single-row tapered roller), heavy-OD section series 03, and bore reference 11 resolving to 55 mm; 120 mm OD and 31.5 mm width are the matching ISO 355 boundary values. The SKF catalogue adds the ISO 355 dimension-series code after the bare number (e.g. 2FB); it is the dimensional series, not a separate part number. At 4,800 r/min reference speed the 32.5 mm-section 30311 is governed thermally by preload and lubricant flow; grease or oil selection should be made against that value, with 5,600 r/min as the mechanical ceiling. Mounting practice for 30311: the rotating cone takes the interference fit (k5 on a 55 mm shaft), the cup slides for axial location, and reversing-thrust duty demands a paired O/X set rather than one bearing.
Typical equipment & failure modes
Common applications
- axle-boxes in material-handling equipment
- automotive and light-truck wheel hubs
- industrial gearbox shafts and reducers
- differential and pinion drives
Known failure patterns
- cup or cone misalignment when the separable rings are not seated square during mounting
- loose cup rotation in the housing when the specified press fit is not achieved
- uneven load sharing in a pair when spacer faces are not parallel to the bore
- thermal preload runaway in an O-arrangement pair when inner-ring heat expands the setting
- pressed-steel cage wear or fracture after prolonged running above the limiting speed
- electrical pitting on VFD-driven shafts without grounding protection
Selection pitfalls — read before you substitute
- On this 55 mm bore, interference and temperature rise consume clearance inside a preloaded pair; calculate the residual clearance after mounting and at operating temperature — an over-tight 30311 pair heats, loses setting control and smears the roller-rib contact.
- The 303 series at 55 mm bore (120×31.5 mm) carries a larger OD and higher capacity than 30211 at the same bore; the bigger section runs hotter, so re-check the 5,600 r/min speed ceiling and shoulder diameters before substituting.
- A single 30311 cannot locate the shaft axially in both directions; mounting it singly on a reversing-thrust shaft leaves one direction uncontrolled — always use an O or X matched pair for bidirectional location.
- At the 176 kN rating of 30311, preload class changes stiffness by tens of percent but also heat generation; select light preload for the 5,600 r/min speed end and heavier preload only where moment stiffness dominates.
- Never press both rings through the wrong element during fitting: force for an interference shaft seat goes through the cone only, or brinell marks on the 120 mm cup race release as noise within the first running hours.
- The 176/163 kN ratings are SKF catalogue 17000 values for the basic 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 and re-verify for critical drives.
- SKF lists several executions of 30311 (basic, B steeper angle, Q/J2 clearance variants); they are not interchangeable order numbers — quote the full SKF 30311 designation when purchasing and match the execution to the mounting arrangement.
Frequently asked questions
What are the dimensions and catalogue data of 30311?
The SKF 30311 is a single-row tapered roller bearing with 55 mm bore, 120 mm outer diameter and 31.5 mm width (2.165 × 4.724 × 1.24 in) per ISO 355. From SKF catalogue PUB BU/P1 17000: basic dynamic load rating C 176 kN, C0 163 kN, fatigue load limit Pu 19.3 kN, reference speed 4,800 r/min, limiting speed 5,600 r/min, mass about 1550 g. It is an open, separable bearing with a pressed-steel cage.
How does the 30311 bore code work?
The last two digits of 30311 are bore code 11, so 11 × 5 = 55 mm bore. The 120 mm OD and 31.5 mm width come from the ISO 355 dimension-series plan, shared with other tapered bearings of the same code.
What do the 30311 series and basic execution designations mean?
The leading 3 marks a single-row tapered roller bearing; the second digit 03 is the ISO 355 series (heavy-OD section). The SKF catalogue lists the ISO 355 dimension-series code after the bare number. A steeper-contact-angle variant (B suffix) is a different order number and is not interchangeable with the basic execution.
Can a single 30311 take axial load in both directions?
No — one single-row tapered roller bearing reacts thrust in one direction only, and under radial load its contact angle induces an axial force. Use two bearings as a matched pair: O (back-to-back) for a rigid, moment-resisting arrangement, X (face-to-face) where thermal expansion must be tolerated, or tandem where one-direction thrust is shared.
How does 30311 compare with a ball bearing of the same bore?
A tapered roller bearing has line contact and a steep contact angle: much higher combined axial-plus-radial capacity and shock resistance than a ball bearing of the same bore, at the cost of speed, one-direction thrust, mandatory pairing for reversing loads and a minimum axial load requirement. A ball bearing cannot be dropped into a combined-load 30311 position and vice versa — verify load direction, Fa/Fr ratio and speed before substituting.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 8.1 metric single-row TRB on 2026-09-26. Read our editorial & correction policy.