Product Overview
King Racing Honda Main Bearings MB5568XP0.25 – Tri-Metal Racing Engine Bearings
The King Racing Honda Main Bearings MB5568XP0.25 are a premium performance crankshaft bearing set engineered for selected Honda D-Series, B20A and F23 engines requiring 0.25mm undersize main bearings.
Designed for high-load engine applications, these King XP Series bearings combine advanced pMaxBlack tri-metal construction, precision-manufactured bearing geometry and specialised lubrication features to support durability in professionally rebuilt performance engines.
Whether you’re rebuilding a Honda Civic D16 engine, preparing a track-focused Honda or restoring an eligible Honda Accord or Prelude engine, choosing the correct main bearings is essential for crankshaft support, oil pressure and long-term reliability.
Why Choose King Racing Honda Main Bearings?
1. Advanced pMaxBlack Tri-Metal Construction
The King Racing XP Series uses a high-performance tri-metal bearing structure designed to support the demanding operating conditions of tuned engines.
The pMaxBlack material incorporates a strengthened copper-based intermediate structure with a hardened bearing overlay.
This construction is engineered to provide improved load-carrying capability and fatigue resistance compared with conventional replacement bearing materials.
King’s XP Series is intended for applications where precise oil clearances and consistent crankshaft support are essential.
2. Correct +0.25mm Size for Reground Crankshafts
The MB5568XP0.25 is a 0.25mm undersize main bearing set.
This means it is intended for a crankshaft whose main journals have been machined approximately 0.25mm smaller in diameter than the original standard specification.
The corresponding bearing shells have additional wall thickness to compensate for the reduced journal diameter.
These bearings must not be fitted to an unmachined standard-size crankshaft unless measurements and the manufacturer’s specification specifically establish compatibility.
Always have the crankshaft measured by an experienced engine machinist before selecting the bearing size.
3. U-Groove Oil Distribution Technology
King’s U-Groove design uses a specially engineered oil groove profile intended to improve effective bearing load area while maintaining oil flow.
A stable lubrication film is particularly important when an engine operates at elevated RPM or under sustained load.
Proper oil clearances, oil pressure and lubrication system condition remain essential.
4. Bull’s Eye Tolerance Manufacturing
King’s Bull’s Eye Tolerance technology is designed to minimise variations in bearing shell wall thickness.
Consistent wall thickness supports predictable bearing clearance and accurate engine assembly.
This is especially valuable during precision Honda engine rebuilding, where small dimensional differences can influence bearing performance.
5. EccentriX and RadiaLock Technologies
King Racing incorporates specialised bearing geometry to support reliable operation.
EccentriX optimises the bearing’s eccentricity to encourage stable hydrodynamic lubrication.
RadiaLock addresses bearing crush height, helping provide the required interference fit between the shells and the main bearing housing.
These features contribute to consistent bearing seating, heat transfer and lubrication when installed within specification.
King Racing MB5568XP0.25 Technical Specifications
The MB5568XP0.25 belongs to the MB5568XP bearing family.
Its key characteristics include:
- XP Racing pMaxBlack tri-metal material
- 0.25mm undersize crankshaft journal application
- Five pairs of main bearing shells
- Full-groove configuration
- Standard-reference journal diameter approximately 54.98–55.00mm
- Standard-reference main housing diameter approximately 59.00–59.02mm
- Bearing width approximately 20.00mm
Note: The reference diameters above are standard catalogue dimensions. They are not the required finished journal specification for the +0.25mm variant. The correct final journal size and oil clearance must be established during machining and assembly.
Honda D16, B20A and F23 Engine Compatibility
King lists the MB5568XP family for several Honda engines, including:
- Honda D16A, D16B, D16W, D16Y and D16Z
- Selected Honda D17A and D17Z
- Honda B20A3 and B20A5
- Honda F23A and F23Z
- Selected Honda H22A and H22Z applications
Engine code, year and original bearing configuration must be checked before ordering.
Important distinction: Honda B20A engines are different from the B20B and B20Z engines used in other Honda models. Likewise, B17A1 uses a different King main bearing reference in the current application guide.
Are King XP Bearings Suitable for Turbocharged Honda Engines?
King XP Racing bearings are developed for demanding performance applications and may be suitable for correctly engineered naturally aspirated or forced-induction engine builds.
However, bearing selection depends on crankshaft dimensions, engine loading, lubrication system performance and the intended operating clearances.
Installing race bearings does not automatically increase horsepower or guarantee greater engine reliability.
A successful engine build requires accurate machining, cleaning, measurement and professional assembly.
Installation and Crankshaft Clearance Requirements
Before installing MB5568XP0.25 bearings, the engine builder should:
- Measure every crankshaft main journal
- Confirm the journal machining and bearing undersize
- Inspect the main bearing housing dimensions
- Check bearing oil clearance at every main journal
- Inspect the crankshaft surface finish
- Verify main bearing alignment
- Confirm the correct thrust washer specification
- Clean oil galleries and mating surfaces
- Follow the engine manufacturer’s fastener and assembly procedures
Incorrect bearing sizing can result in inadequate lubrication, excessive clearance, crankshaft damage or premature engine failure.
Buy King Racing Honda Main Bearings in the UK
At Performance Car Parts UK, we supply performance engine components for Honda enthusiasts, motorsport customers and professional engine builders.
Choosing the correct crankshaft bearing size is essential for any performance engine rebuild, particularly where increased engine loads and tighter machining tolerances are involved.
If you’re planning a broader engine upgrade, our Fuel Pump and Injector Upgrade Guide explains additional considerations when increasing engine output.
For official bearing application data, see the King Racing 2025–2026 Application Guide.
You can also review the King Engine Bearings MB5568XP product family, including available sizes and bearing specifications.
Order King Racing MB5568XP0.25 Honda Tri-Metal Main Bearings from Performance Car Parts UK for your next professionally prepared engine rebuild.
Always confirm the exact Honda engine code, crankshaft dimensions, bearing size and required oil clearance before purchasing.
