King Engine Bearings MB5304XP05 XP Series Tri-Metal Main Bearing Set - 0.5mm

The King Engine Bearings MB5304XP0.5 is a +0.5mm oversize XP Series tri-metal crankshaft main bearing set engineered for high-load, high-RPM performance and racing applications using steel crankshafts. Designed for Mazda B6, B6-T, ZM, B3, and B5 engines, this set delivers race-proven durability with advanced metallurgical and geometric technologies far beyond standard replacement bearings.

pMaxBlack™ Tri-Metal Construction:

• pMaxBlack™ overlay — contains 5% copper and undergoes a proprietary nano-scaled hardening process that modifies the molecular structure, creating a fatigue-resistant shield. The result is a 29% increase in overlay hardness (18.1 HV) and a 24% increase in load capacity, reaching 10,200 PSI — significantly outperforming conventional race bearing overlays rated at 8,000–8,500 PSI
• Enhanced copper-lead intermediate layer — increased tin content (4.5%) delivers 115 HV hardness and an intermediate load capacity of 17,000 PSI
• SecureBond™ adhesion process — micro-etch surface preparation that strengthens tri-metal structural integrity and reduces the risk of delamination under extreme load or metal-to-metal contact
• 15%–30% greater load capacity than traditional bearings
• 0.0005" hardened performance overlay resists surface fatigue under sustained high-load conditions

Precision Geometry Features:

• Bull's Eye Tolerance™ — industry-leading wall thickness consistency with all shells matched to ±0.0001", reducing the need to purchase multiple sets to achieve desired oil clearance
• 1/2-groove main design — upper shells are half-grooved to preserve lower shell load capacity while maintaining consistent oil distribution
• Enlarged, chamfered oil holes on main bearings for improved oiling across the full bearing surface
• Medium eccentricity (EccentriX™) — optimized eccentricity value for each bearing promotes stable hydrodynamic lubrication and even load distribution
• Narrowed design — mains are narrowed to clear large-radius aftermarket crankshafts

Ideal Applications:

• Circle track, drag racing, off-shore, and off-road racing
• High-load, long-duration performance builds using forged steel aftermarket crankshafts
• Any performance application demanding sustained high-RPM and high-load capacity

King Engine Bearings has specialized exclusively in engine bearings since 1960, offering the industry's widest selection of sizes and clearance options. The XP Series represents the pinnacle of King's tri-metal performance lineup — engineered, tested, and validated through King's in-house TechLab R&D program.