ACL 6B1584H-.25 +0.25 mm Oversize Rod Bearing Set for BMW N54 / N55 / S55

Vehicle Fitment

• BMW 3.0 L Inline-6: N54B30 (e.g., 335i, 135i)
• BMW 3.0 L Inline-6: N55B30 (e.g., 335i, 535i)
• BMW 3.0 L Inline-6: S55B30 (e.g., M3, M4)

Features

• Race-series tri-metal construction for high strength and fatigue resistance
• +0.25 mm oversize specification for precision fit on machined or worn crankshafts
• Hardened steel backing improves bearing structural support
• Increased eccentricity supports hydrodynamic oil film at high RPM
• Raised crush height ensures better bearing retention during engine operation
• No flash plating on the back improves heat transfer into the housing
• Tight, consistent wall tolerances for reliable and uniform oil clearances
• Identical upper and lower shells for simplified assembly and balanced fitment

Specifications

• Part Number: 6B1584H-.25
• Bearing Size: +0.25 mm oversize
• Oil Clearance: Standard / Race spec
• Half-Shell Type: Identical upper / lower
• Material: Tri-metal (steel backing, copper-lead intermediate, lead/tin overlay)
• Max Shaft Diameter: ~49.993 mm
• Max Tunnel (Housing) Diameter: ~53.616 mm
• Max Wall at Crown: ~1.793 mm
• Max Overall Shell Length: ~17.55 mm

Included Components

• 6x rod bearing shells (complete set for one inline-6 engine)

Product Description

The ACL 6B1584H-.25 is a premium, race-series rod bearing set designed for BMW 3.0 L twin-turbo and high-rev inline-6 engines (N54, N55, and S55). Its +0.25 mm oversize specification is ideal for engines with crankshafts that have been machined, worn, or require tighter clearances for high-performance builds.

Built with tri-metal materials, these bearings deliver excellent fatigue resistance and durability under extreme RPM and load conditions. The hardened steel backing and increased eccentricity help to maintain a stable hydrodynamic oil film, critical for performance and longevity. The raised crush height keeps the bearings firmly in place even under high stress.

Whether you're building a modified street motor, a track engine, or a high-output turbo build, this bearing set ensures reliable oiling, tight clearances, and long-lasting performance for your BMW N54, N55, or S55 inline-6 engine.