ACL 5M1959H-.025 Race Main Bearing Set +0.025mm Honda B16A B18C K20A2 K24A RSX

Vehicle Fitment

• 1989-2001 Honda Civic / CRX / Del Sol - B16A variants (1.6L DOHC VTEC)
• 1992-1993 Acura Integra GS-R (B17A1, 1.7L DOHC VTEC)
• 1990-2001 Acura Integra GS/LS/RS (B18A1/B18B1/B18B2, 1.8L DOHC)
• 1994-2001 Acura Integra GS-R / Type-R (B18C1/B18C5, 1.8L DOHC VTEC)
• 1997-2001 Honda CR-V (B20B / B20Z, 2.0L DOHC)
• 2002-2005 Honda Civic Si EP3 (K20A3, 2.0L DOHC i-VTEC)
• 2002-2006 Acura RSX / RSX Type-S (K20A3 / K20A2, 2.0L DOHC i-VTEC)
• 2003-2007 Honda Accord (K24A, 2.4L DOHC i-VTEC)
• 2002-2014 Honda CR-V (K24A, 2.4L DOHC i-VTEC)
• 2003-2011 Honda Element (K24A, 2.4L DOHC i-VTEC)
• 2004-2008 Acura TSX (K24A2, 2.4L DOHC i-VTEC)
• 2007-2012 Acura RDX (K23A1, 2.3L DOHC Turbo)

Fitment Notes

• The .025 suffix designates this as the +0.025mm oversize bearing set - for use when the crankshaft main journals have been ground 0.025mm undersize. K Series Parts describes this as equivalent to a Honda green bearing with an extra 0.025mm of thickness, restoring correct running clearance on a lightly reground crank. For standard journal diameter, use 5M1959H-STD. For crankshafts ground 0.25mm undersize, use 5M1959H-.25.
• This single set covers both the Honda/Acura B-series (B16A through B20Z) and K-series (K20A2/A3/Z1, K24A/A2/Z1) inline-4 engines - all share the same crankshaft main journal dimensions despite differences in displacement and application.
• Always measure crankshaft main journal diameter with a micrometer before selecting bearing size. Confirm actual clearance with Plastigage or a dial bore gauge after assembly.
• Sold as a complete set of 10 bearing shells (5 pairs, upper and lower) - sufficient for all 5 main journal positions in one 4-cylinder engine.

Features

• Tri-metal construction: copper-lead alloy lining bonded over a hardened steel backing, with a high-strength overlay plate - engineered for the high-RPM and forced-induction demands of performance-built Honda B-series and K-series engines.
• Hardened steel backing on all main bearings improves structural support of the bearing lining and maintains crush under elevated crank loads in high-power B-series and K-series builds.
• High-strength overlay plate with reduced thickness provides improved fatigue resistance compared to OEM-spec bearings - critical in boosted or sustained high-RPM applications across both engine families.
• Increased bearing crush and tighter wall tolerances ensure consistent, secure seating in the block main journal bores, reducing the risk of bearing movement.
• Enlarged ID chamfers on bearing edges accommodate the larger fillet radii found on performance and aftermarket Honda crankshafts.
• 3/4-groove upper main bearings optimize oil supply to the main journals and to the connecting rod bearings through the crankshaft oiling passages.
• Elimination of flash plating on bearing backs improves heat transfer and maximizes grip between the bearing shell and the block main bore.
• Increased eccentricity compensates for bore distortion at high RPM and assists in the formation of a stable hydrodynamic oil film under load.

Specifications

• Part Number: 5M1959H-.025
• Product Line: ACL Race Series
• Application: Crankshaft Main Bearings
• Engine Compatibility: Honda/Acura B16A variants (1595cc); B17A1 (1678cc); B18A1, B18B1, B18B2 (1834cc); B18C1, B18C2, B18C5, B18C7 (1797cc VTEC); B20B, B20Z (1972cc); K20A2, K20A3, K20Z1 (1998cc); K24A, K24A2, K24Z1 (2354cc)
• Crankshaft Size: +0.025mm Oversize (for main journals ground 0.025mm undersize)
• Shaft (Main Journal) Diameter: 54.955-54.975mm (2.1636-2.1644 in)
• Tunnel (Housing Bore): 59.000-59.020mm (2.3228-2.3236 in)
• Maximum Wall Thickness at Crown: approx. 2.015mm (0.0793 in)
• Maximum Overall Length: 20.0mm (0.787 in)
• Bearing Material: Tri-Metal Copper-Lead Alloy / Hardened Steel Backing
• Quantity: Set of 10 Shells - 5 Upper + 5 Lower (complete engine set)

Included Components

• 10x Race Series Crankshaft Main Bearing Shells - +0.025mm Oversize (5 upper, 5 lower)

Product Description

The ACL Race Series 5M1959H-.025 crankshaft main bearing set is the +0.025mm oversize option for Honda/Acura's broad B-series and K-series inline-4 engine family - one of the widest-spanning main bearing sets in the ACL catalog, covering everything from the B16A-powered Civic and CRX to the B18C Type-R Integra, B20B CR-V, and the full K20/K24 lineup found in the RSX, Civic Si, Accord, Element, and TSX. All of these engines share identical crankshaft main journal dimensions, making this a single set for any of them at the +0.025mm oversize step.

This oversize set is selected when the crankshaft main journals have been ground 0.025mm undersize to address light surface wear or achieve a specific clearance target. K Series Parts describes it as equivalent to a Honda green bearing with an extra 0.025mm of wall thickness. Built on ACL's Race Series tri-metal platform, these main bearings deliver superior fatigue resistance and oil film stability over OEM Honda shells. Always confirm clearances at assembly. Sold as a complete set of 10 shells for one engine.