RNA4912-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 RNA4912-XL model number is decoded

envelope 68×85×25 mm: 68 mm seat is the hardened and ground shaft journal itself — there is no inner ring, with a thin 8.5 mm radial section packed with small-diameter needle rollers C is 68 kN and C0 108 kN at the 68 mm seat; the C/C0 ratio of 0.63 is characteristic of a needle bearing — high static rating relative to dynamic in a compact 85 mm outside diameter the fatigue load limit Cur is 19.1 kN, the limiting speed 6,700 r/min and the thermal reference speed 3,850 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 1.00 kN/mm and per millimetre of width 2.72 kN/mm — the reason 25 mm-wide needle bearings routinely replace much larger ball or roller positions mass is 275 g, just 0.13 g per mm² of projected 85×25 mm envelope, which keeps unbalanced forces low in fast-actuating linkages at 68 mm bore the 85 mm outside diameter and 25 mm width target rolling stands, construction machinery and heavy gearboxes; the limiting speed drops to 6,700 r/min 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 RNA4912-XL has no inner ring: the needle rollers run directly on the shaft journal, so the seat must be hardened (58–64 HRC) and ground to bearing raceway quality -XL means this is an X-life bearing — Schaeffler's upgraded performance level with smoother raceways, so the 68 kN C rating and longer nominal life come without an envelope change. Typical applications include two-stroke and compressor piston pins, motorcycle and light-vehicle transmissions and rocker arms and valve trains, where the 85 mm outside diameter and 68 kN dynamic rating match the duty. In two-stroke and compressor piston pins the unit fits a compact 68 mm seat, and in motorcycle and light-vehicle transmissions the 275 g mass keeps unbalanced forces low in fast linkages. Designers also specify it for rocker arms and valve trains, relying on the 25 mm width and the published 108 kN static rating. Without an inner ring the shaft is the raceway: 58–64 HRC and a ground, polished journal are mandatory, not recommendations. 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

• Without an inner ring the shaft is the raceway: 58–64 HRC and a ground, polished journal are mandatory, not recommendations.
• 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.
• On reciprocating duty ensure the stroke rotates the full needle set, or brinelling occurs at the same roller positions.