What is the purpose of main bearings?

Main bearings support the crankshaft within the engine block. They create a low-friction surface for the crankshaft to rotate on, and they maintain the correct oil clearance to ensure proper lubrication and prevent excessive wear.

Why would I need an oversize bearing set like this +0.25mm set?

Oversize bearings are used when the crankshaft journals have been machined down to correct wear or out-of-round conditions. The +0.25mm size indicates that the crankshaft journals have been reduced in diameter by 0.25mm, and these bearings are designed to restore the original factory oil clearance.

What is the XP-3 material used on these bearings?

XP-3 is a specialized tri-metal overlay material developed by King Engine Bearings. It is known for its strong wear resistance and ability to handle high loads, making it suitable for performance applications and engine rebuilds where durability is important.

Specifications

Brand: King Engine Bearings
Part #: MB7776GPC0.25
UPC: 611500626739

King Engine Bearings BMW N55 B30A/ N53 B30A/ N52 B30A Main Bearing Set - Size +0.25mm

Name: King Engine Bearings BMW N55 B30A/ N53 B30A/ N52 B30A Main Bearing Set - Size +0.25mm
Brand: King Engine Bearings
SKU: king-engine-bearings-king-engine-bearings-bmw-n55-b30a-n53-b30a-n52-b30a-main-be-t14-432599
Price: 273.86 USD
Availability: BackOrder

$273.86

On Backorder — Expected to ship by Sep 16, 2026

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King Engine Bearings main bearing set for BMW N55 B30A, N53 B30A, N52 B30A engines. Size +0.25mm.

Key Features

Fits BMW N55 B30A, N53 B30A, and N52 B30A engines.
Main bearing set is +0.25mm oversize for machined crankshaft journals.
Features King's XP-3 tri-metal overlay material for improved durability.
Designed to maintain proper oil clearance and support the crankshaft.

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About this part

Product Details

This is a main bearing set from King Engine Bearings, specifically sized at +0.25mm for BMW N55 B30A, N53 B30A, and N52 B30A engines. Main bearings are crucial for supporting the crankshaft within the engine block, ensuring it spins smoothly and with minimal friction. When rebuilding or repairing an engine, especially one with higher mileage or performance modifications, replacing these bearings is a common and important step to restore proper oil clearance and bearing surface integrity.

King Engine Bearings uses a specialized overlay material called XP-3, which is a tri-metal material known for its durability and ability to handle high loads. This overlay is designed to resist wear and maintain its properties under demanding conditions. The bearings are manufactured to precise tolerances, and this particular set is +0.25mm oversize, meaning it's intended for crankshaft journals that have been machined down by 0.25mm to correct wear or out-of-round conditions. Proper installation, including ensuring the crankshaft journals are clean and within the specified machining tolerance, is key to achieving the correct oil clearance and ensuring the longevity of your engine rebuild.