NK85-25-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 NK85-25-XL model number is decoded

envelope 85×105×25 mm: 85 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 10.0 mm radial section packed with small-diameter needle rollers C is 78 kN and C0 123 kN at the 85 mm seat; the C/C0 ratio of 0.63 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 105 mm outside diameter the fatigue load limit Cur is 22.1 kN, the limiting speed 5,400 r/min and the thermal reference speed 3,550 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 0.92 kN/mm and per millimetre of width 3.12 kN/mm — the reason 25 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 425 g, just 0.16 g per mm² of projected 105×25 mm envelope, which keeps unbalanced forces low in fast-actuating linkages the 85 mm bore belongs to the large band, where HR1 full-complement and track-roller designs deliver their highest kilonewton ratings in slow, heavily loaded machinery This bearing accepts axial displacement between shaft and housing because the rollers rotate on the free journal; it locates nothing axially and must be flanked by guide faces With Cur 22.1 kN and a 5,400 r/min limiting speed the unit suits pivots, rocker arms, pumps and compact gear trains running on hardened pins As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 22.1 kN Cur value. Typical applications include rocker arms and valve trains, two-stroke and compressor piston pins and small electric motor accessory drives, where the 105 mm outside diameter and 78 kN dynamic rating match the duty. In rocker arms and valve trains the unit fits a compact 85 mm seat, and in two-stroke and compressor piston pins the 425 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for small electric motor accessory drives, relying on the 25 mm width and the published 123 kN static rating. Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone. Do not press an RNA/NK assembly in through the outer ring when mounting it on a shaft, and vice versa — rolling forces through the wrong ring bruises the raceways.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Open ends draw contamination directly onto the needles; specify sealed or shielded positions in dusty environments rather than relying on grease alone.
• Do not press an RNA/NK assembly in through the outer ring when mounting it on a shaft, and vice versa — rolling forces through the wrong ring bruises the raceways.
• Needle bearings are pure-radial units — any thrust must be taken by separate washers or an adjacent bearing, especially on flangeless RNAO/NAO.