NKI38-30-XL bearing: complete specifications & equivalents

Specification table

Source: catalog reference (HR1 2026-09-25) · extracted 2026-09-30

Parameters extracted from the official FAG Rolling Bearings catalogue (HR1 2026-09-25); FAG® is a trademark of Schaeffler Technologies AG & Co. KG, used here for identification only — mpnbase is not an authorized FAG/Schaeffler distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at schaeffler.com.

Cross references & equivalents

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 NKI38-30-XL model number is decoded

envelope 38×53×30 mm: 38 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 7.5 mm radial section packed with small-diameter needle rollers C is 45.5 kN and C0 85 kN at the 38 mm seat; the C/C0 ratio of 0.54 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 53 mm outside diameter the fatigue load limit Cur is 16.1 kN, the limiting speed 10,700 r/min and the thermal reference speed 5,900 r/min; for small needle bearings the reference speed can exceed the kinematic limit, so the lower of the two governs the application dynamic capacity per millimetre of bore is 1.20 kN/mm and per millimetre of width 1.52 kN/mm — the reason 30 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 207 g, just 0.13 g per mm² of projected 53×30 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 38 mm bore this is a mainstream industrial size — conveyor drives, winches and medium gearboxes use the 30 mm width as a standard mounting space This is the choice for OEM production on soft shafts: machine the 38 mm seat to the recommended tolerance, fit the bearing, and let the inner ring provide the precision raceway Reading the NKI prefix: machined-ring needle bearing with inner ring, one roller row, capable of pure radial load at 45.5 kN C -XL means this is an X-life bearing — Schaeffler's upgraded performance level with smoother raceways, so the 45.5 kN C rating and longer nominal life come without an envelope change. Typical applications include motorcycle and light-vehicle transmissions, connecting-rod small ends and two-stroke and compressor piston pins, where the 53 mm outside diameter and 45.5 kN dynamic rating match the duty. In motorcycle and light-vehicle transmissions the unit fits a compact 38 mm seat, and in connecting-rod small ends the 207 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for two-stroke and compressor piston pins, relying on the 30 mm width and the published 85 kN static rating. Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO. Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO.
• Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.
• Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.