MPNbase

40×90×25.25 mm bearings

5 models from 2 brands across 1 type share this ISO 15 envelope: 40 mm bore, 90 mm outside diameter, 25.25 mm width (1.575×3.543×0.994 in), 25 mm radial section.

5 models fit this space 2 brands 5 with catalogue C rating

Dimensional interchange — verify before substituting

These bearings are interchangeable on boundary dimensions per ISO 15 — same bore, OD and width. They are not guaranteed drop-in equivalents: compare load ratings, seals, clearance, cage, precision and axial-locating design for the specific duty. Models without a catalogue C rating on this site carry ISO 15 geometry only; request the manufacturer table before a load-critical replacement.

Model Type Brand Seal Clearance C (kN) C0 (kN) Mass (g)
30308 Tapered Roller SKF open CN 106 95 730
30308-NTN Tapered Roller NTN open CN 101 102 765
30308C Tapered Roller NTN open CN 92 87 726
30308D Tapered Roller NTN open CN 85.5 85.5 727
31308 Tapered Roller SKF open CN 91.1 81.5 720

Note: catalogue dynamic load ratings for this envelope span 85.5– 106.0 kN — a 24% spread between designs in the very same 40×90×25.25 mm space. The higher-rated unit is not an upgrade for every duty (it may run at lower limiting speed), but ignoring the gap will over- or under-life the replacement.

Substitution verification checklist

  1. Load rating. Check C (dynamic) and C0 (static) against the original life calculation — the table above shows which models carry verified catalogue values.
  2. Sealing. Open, -ZZ shields and -2RS contact seals are not equivalent in friction, speed or contamination protection; match the housing environment, not just the suffix on the old box.
  3. Internal clearance. CN/C3/C4 changes with fit and operating temperature; an interference inner-ring mount commonly needs C3 where the bench bearing ran CN.
  4. Cage and precision. Stamped steel, machined brass and polymer cages, and P0/P6/P5 tolerance classes, carry different speed and shock limits.
  5. Locating behaviour. Within one envelope an NU cylindrical roller floats axially while an NJ/NUP locates; ball designs take thrust that roller locating schemes do not. Preserve the shaft's locating arrangement.

Browse all 40 mm bore bearings for wider or narrower sections, or open a model page for naming-rule decode, applications and graded cross references: 30308, 30308-NTN, 30308C, 30308D, 31308.

Frequently asked questions

Are all 40×90×25.25 mm bearings interchangeable?

They share the same ISO 15 boundary dimensions — 40 mm bore, 90 mm OD, 25.25 mm width (1.575×3.543×0.994 in) — so they fit the same shaft, housing bore and axial space. Interchangeability ends at the envelope: dynamic load rating, seal arrangement, internal clearance, cage and precision class differ between the 5 models listed here and must be checked against the duty before substitution.

Is it a drop-in replacement if two bearings both measure 40×90×25.25?

Only after verification. Confirm five things in order: (1) the C/C0 load ratings meet the original life calculation, (2) the seal type is equivalent or acceptable for the contamination level (open vs -ZZ vs -2RS), (3) internal clearance matches (CN/C3/C4 — an interference fit changes residual play), (4) cage material and precision class suit the speed, and (5) the axial-locating behaviour is the same (for example an NU cylindrical roller floats while an NJ locates one way). Same dimensions alone never guarantee equal performance.

What is 40×90×25.25 mm in inches?

40×90×25.25 mm converts to 1.575×3.543×0.994 in, with a 25 mm (0.984 in) radial section height. These are the ISO 15 general-plan envelope dimensions shared across manufacturers, which is why models such as 30308, 30308-NTN, 30308C mount in the same space despite different internal designs.