NKI55-25-TV-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 NKI55-25-TV-XL model number is decoded

envelope 55×72×25 mm: 55 mm bore accepts a normal-tolerance machined shaft via the integral inner ring, with a thin 8.5 mm radial section packed with small-diameter needle rollers C is 53 kN and C0 103 kN at the 55 mm seat; the C/C0 ratio of 0.51 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 72 mm outside diameter the fatigue load limit Cur is 17.8 kN, the limiting speed 7,700 r/min and the thermal reference speed 4,400 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 0.96 kN/mm and per millimetre of width 2.12 kN/mm — the reason 25 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 255 g, just 0.14 g per mm² of projected 72×25 mm envelope, which keeps unbalanced forces low in fast-actuating linkages 55 mm bore marks the medium range: mounting forces and fits become critical, and the 255 g mass calls for proper induction or press tooling rather than hand fitting Reading the NKI prefix: machined-ring needle bearing with inner ring, one roller row, capable of pure radial load at 53 kN C Cur 17.8 kN, limiting speed 7,700 r/min, reference speed 4,400 r/min — the inner ring adds a few grams (total 255 g) but removes the hardening requirement As an X-life (-XL) bearing it benefits from the optimised surface finish that reduces friction and raises the fatigue strength behind the 17.8 kN Cur value. The -TV suffix specifies a glass-fibre reinforced polyamide 66 window-type cage; it spaces the rollers for low friction and is the reason the limiting speed can reach 7,700 r/min. Typical applications include gearbox selector and change linkages, planetary gear bearings and copying and printing machine mechanisms, where the 72 mm outside diameter and 53 kN dynamic rating match the duty. In gearbox selector and change linkages the unit fits a compact 55 mm seat, and in planetary gear bearings the 255 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for copying and printing machine mechanisms, relying on the 25 mm width and the published 103 kN static rating. Adding an IR inner ring changes the envelope logic: the same outer assembly then fits a smaller shaft — recheck bore, clearance and ratings when substituting. Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Adding an IR inner ring changes the envelope logic: the same outer assembly then fits a smaller shaft — recheck bore, clearance and ratings when substituting.
• Keep the specified radial clearance; an oversized shaft or heavy interference removes it and the needles bind hot immediately.
• 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.