30218 bearing: complete specifications & equivalents
The 30218 is a ISO 355 radial bearing sized 90 x 160 x 32.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Bore diameter d | 90 mm |
| Outer diameter D | 160 mm |
| Width B | 32.5 mm |
| Seal / shield | open |
| Internal clearance | CN available |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Operating temperature | -30 to +120 °C |
| Mass (geometry estimate) | 2279 g |
| Standard | ISO 355 |
| Catalog version | iso355-geometry |
| Last verified | 2026-09-24 |
Source: ISO 15 boundary-dimensions standard · extracted 2026-09-24
Standard-interchange bearing: dimensions per ISO 15; CN clearance, P0 tolerance and a stamped-steel cage are catalogue defaults unless the supplier states otherwise, and mass is a geometry-derived estimate. Brand catalogue load ratings and limiting speeds for 30218 are being backfilled — use the inquiry form for certified values.
Dimensions in inches & 30200-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 6.299 in |
| Width B | 1.28 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 35 mm |
| Smallest bore in 30200-series | 20 mm |
| Largest outer diameter in 30200-series | 200 mm |
| Width range across 30200-series | 15.25–41 mm |
| Bore position in 30200-series (smallest first) | 15 of 19 |
| Bore above smallest 30200-series size | 70 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 30218 | 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 30218 model number is decoded
In the 30200-series the last two digits of 30218 encode the bore: code 18 = 90 mm (code × 5 from 04 upward). The ISO 355 envelope is 160 mm outside diameter and 32.5 mm total assembly width T over the separable cone and cup — 3.543 × 6.299 × 1.28 in, with a 35.0 mm radial section height. Tapered rollers carry combined radial and single-direction axial load; bidirectional thrust needs an opposed pair (X face-to-face or O back-to-back) adjusted at fit-up. With a rotating cone on a 90 mm shaft, typical catalogue practice is a k5 shaft seat with an H7 housing bore, EP lubrication and a defined end-play setting — verify against the load direction and magnitude.
Typical equipment & failure modes
Common applications
- truck and trailer wheel hubs
- heavy final drives and differentials
- large conveyor drum pulleys
- crane travel wheels and winch drums
- railway axle boxes
Known failure patterns
- over-preload heat: a shim stack cut too thin drives contact stress up and seizes the cone on the seat
- under-preload end play that lets the rollers skid, producing noise and false brinelling
- water and grit pitting in unsealed hubs where the cup-cone joint acts as a debris entry path
- false brinelling from vibration while the axle is stationary during transport
- fretting corrosion on a loose shaft seat when the cone is pressed to an interference that relaxes with wear
Selection pitfalls — read before you substitute
- The large 90 mm-bore 30218 develops substantial mounting forces; heat the cone (induction heater, max 120 °C) and never tighten the adjusting nut to seat it — draw it up by torque, then back off to the mark, leaving roughly 0.05–0.20 mm end play on the 90 mm shaft.
- The 302 light series at 90 mm bore (160×32.5 mm, 35.0 mm section) is the default general-purpose tapered row; a 32218 on the same 90 mm bore uses the same OD but a wider section for heavier load — it is not a like-for-like width swap.
- The 32.5 mm-wide 30218 ring seats against a shaft and housing shoulder whose fillet must clear the bearing chamfer: keep the corner radius small enough that the 90 mm bore and 160 mm cup seat square — an undercut beats an oversized radius, which lifts the ring and edge-loads the 35.0 mm section.
- When mounting 30218 to a 90 mm shaft, warm the cone to 80–100 °C and slide it dry to the shoulder; cooling shrinks it into its interference, whereas hammering a cold cone through a 160 mm assembly dents the tapered raceway before first run.
- Relubrication for 30218 must reach the rib-roller end contact, not just the 90 mm bore; in a hub repack, work EP grease through the roller set until it exudes at both faces of the 32.5 mm-wide assembly or the sliding rib contact starves first.
- Set running clearance (or preload) with the shim pack or adjusting nut at fit-up; a 90 mm-bore 30218 that is too tight overheats and scores the rib, one too loose develops end play and noise — follow the torque-and-untighten procedure.
- The sliding contact between roller large ends and the inner-ring rib needs extreme-pressure lubricant; use an EP gear oil or EP grease (GL-5 class in axles) rather than plain bearing grease or the rib will smear in the first heavy run.
Frequently asked questions
What are the dimensions of a 30218 tapered roller bearing?
A 30218 single-row metric tapered roller bearing per ISO 355 has a 90 mm bore, 160 mm outer diameter and 32.5 mm total assembly width (3.543 × 6.299 × 1.28 in), a 35.0 mm radial section and roughly 2279 g geometry-based estimated mass; catalogue masses vary with roller and cage design.
How does the 30218 bore code work?
The last two digits of 30218 are bore code 18, giving 18 × 5 = 90 mm bore — the same convention as 6xx ball bearings, starting at code 04 (20 mm). The 160 mm OD and 32.5 mm width come from the ISO 355 diameter and width series, not the bore code alone.
What is the cone and cup of 30218?
Tapered roller bearings are separable: the cone is the inner ring with the tapered rollers and cage, the cup is the outer ring. 30218 denotes a matched cone-and-cup set. They are fitted separately — cone pressed on the shaft, cup in the housing — and adjusted against each other.
How is the preload or clearance of 30218 set?
At fit-up the 90 mm-bore cone is tightened against the cup while the hub is rotated, seated, then backed off to the specified end play — a typical starting range of 0.05–0.20 mm for a 90 mm bore — and locked with shims, a locknut or a spacer. Too tight overheats and seizes the rib; too loose causes skid, noise and early wear. Confirm the exact figure in the hub or axle-maker procedure.
Can 30218 take axial load in both directions?
A single 30218 takes thrust in one direction only — the roller large ends bear against the inner-ring rib under load. Bidirectional axial load requires an opposed pair: X (face-to-face) tolerates misalignment slightly better, O (back-to-back) gives a wider load centre and more moment stiffness.
Reviewed & verified by the MPN Base engineering desk against source catalog iso355-geometry on 2026-09-24. Read our editorial & correction policy.