King Engine Bearings BMW B58B30A Main Bearing Set | XPC Coated Performance | 0.26mm Undersize | MB7779XPC.026
King Engine Bearings BMW B58B30A Main Bearing Set – XPC Coated Performance | 0.26mm Undersize | MB7779XPC.026
King Engine Bearings’ XPC coated performance main bearing set for the BMW B58B30A 3.0L turbocharged inline-six — in 0.26mm undersize for use with a reground crankshaft. King is the benchmark aftermarket bearing manufacturer for performance and race engine builds, and the XPC coated bearing is their premium street/track/race offering: a tri-metal bearing shell with King’s proprietary XPC polymer coating applied to the bearing surface for reduced friction, improved oil film retention, and enhanced protection during cold starts and transient oil pressure events.
Critical: This is a 0.26mm undersize bearing — for use only with a crankshaft that has been precision-ground 0.26mm undersize on the main journals. Do not install undersize bearings on a standard (unground) crankshaft. Confirm your crankshaft’s journal diameter with a micrometer before ordering. If your crank has not been reground, order the standard size (STD) bearing set instead.
King XPC Coating — What It Is and Why It Matters
King’s XPC (eXtreme Performance Coating) is a polymer coating applied to the bearing surface — a thin, low-friction layer that provides several meaningful performance benefits over an uncoated bearing:
- Reduced Friction: The XPC coating’s low coefficient of friction reduces parasitic power loss at the crankshaft journals — a measurable benefit on a high-revving, high-output B58 build
- Improved Oil Film Retention: The coating’s surface texture retains oil film more effectively than an uncoated bearing surface — maintaining a protective oil film between the bearing and journal during cold starts, high-load transients, and brief oil pressure drops
- Enhanced Wear Protection: The XPC coating provides a sacrificial wear layer that protects the underlying bearing material during the brief periods of metal-to-metal contact that occur during cold starts before full oil pressure is established — the highest-wear event in an engine’s operating cycle
- Conformability: King’s tri-metal bearing construction with XPC coating provides excellent conformability to minor journal surface irregularities — important on a high-mileage or reground crank where the journal surface may not be perfectly uniform
BMW B58B30A — Platform Context
The BMW B58B30A is BMW’s 3.0L turbocharged inline-six — the successor to the N55, introduced in 2016 and used across BMW’s G-chassis lineup and in the Toyota GR Supra A90 (as the B58B30O1 variant). The B58 is a highly regarded engine with a strong aftermarket and significant tuning potential — capable of 500+ hp on the stock block with supporting modifications. On a serious B58 build, King XPC coated bearings are a standard upgrade during engine assembly or rebuild — providing the bearing quality and coating protection that a high-output, high-boost B58 demands.
Key Features
- Main Bearing Set: Complete set of main (crankshaft) bearings for the B58B30A — covers all main journal positions. Rod bearings are sold separately
- 0.26mm Undersize: For use with a crankshaft precision-ground 0.26mm undersize on the main journals. Confirm journal diameter before ordering
- XPC Polymer Coating: King’s proprietary low-friction polymer coating for reduced friction, improved oil film retention, and enhanced wear protection
- Tri-Metal Construction: Steel-backed, copper-lead intermediate layer, and aluminium-tin overlay — King’s proven tri-metal bearing construction for high-load performance applications
- King Engine Bearings: The benchmark aftermarket bearing manufacturer for performance and race engine builds — used by professional engine builders and race teams globally
Common B58B30A Applications
- BMW M240i / M240i xDrive (G42, G43) — B58B30A
- BMW M340i / M340i xDrive (G20, G21) — B58B30A
- BMW M440i / M440i xDrive (G22, G23, G26) — B58B30A
- BMW Z4 M40i (G29) — B58B30A
- BMW 540i / 540i xDrive (G30) — B58B30A
- BMW 640i / 640i xDrive (G32) — B58B30A
- BMW 740i / 740i xDrive (G11, G12) — B58B30A
- Toyota GR Supra A90 (2019+) — B58B30O1 (B58 variant)
Verify your specific engine code and crankshaft journal diameter before ordering. The GR Supra uses a B58 variant (B58B30O1) — confirm bearing compatibility with King’s fitment guide for the Supra application. This is a 0.26mm undersize bearing — do not install on a standard crankshaft.
Specifications
- Brand: King Engine Bearings
- Part Number: MB7779XPC.026
- Type: Main Bearing Set
- Engine: BMW B58B30A 3.0T
- Size: 0.26mm Undersize
- Coating: XPC (eXtreme Performance Coating)
- Construction: Tri-Metal
- Includes: Complete main bearing set (all positions)
Important: Undersize bearings require a precision-ground crankshaft. Measure all main journal diameters with a micrometer before ordering. Engine bearing installation requires precise clearance measurement with Plastigage or a micrometer — professional engine building experience or a qualified engine builder is required. Incorrect bearing clearance will result in premature bearing failure and engine damage.