What is the purpose of main bearings in an engine?

Main bearings support the crankshaft within the engine block. They create a precise clearance for the crankshaft to rotate smoothly while maintaining oil pressure to lubricate the surfaces.

What does '0.75mm undersize' mean for these bearings?

This means the bearings are manufactured to be 0.75 millimeters smaller in diameter than standard size. This size is used when the crankshaft journals have been machined down by 0.75mm to correct wear or damage.

What is the bimetal construction with an aluminum base?

Bimetal bearings typically have a steel backing for strength and a bearing material overlay. In this case, the aluminum base provides good thermal conductivity and wear characteristics, helping to manage heat and friction.

Specifications

Brand: King Engine Bearings
Part #: MB798AM0.75
UPC: 611500183829

King Engine Bearings BMW M20B20-23-25-27 / M50B25 / M52B20-25-28 (Size 0.75) Main Bearing Set

Name: King Engine Bearings BMW M20B20-23-25-27 / M50B25 / M52B20-25-28 (Size 0.75) Main Bearing Set
Brand: King Engine Bearings
SKU: king-engine-bearings-king-engine-bearings-bmw-m20b20-23-25-27-m50b25-m52b20-25-2-t14-495103
Price: 107.03 USD
Availability: BackOrder

$107.03

On Backorder

Order now to reserve yours — we'll ship as soon as stock arrives. Full refund if we're unable to fulfill.

King Engine Bearings Main Bearing Set MB798AM0.75. Fits many BMW M20, M50, and M52 engines. 0.75mm undersize.

Key Features

Fits 1998-2000 BMW 323Ci, 1998-2000 BMW 323i, 1998-1999 BMW 323is, 1986-1988 BMW 325, 1984-1987 BMW 325e, 1986-1987 BMW 325es, 1987-1995 BMW 325i, 1988-1991 BMW 325iX, 1987-1995 BMW 325is, 2000 BMW 328Ci, 1996-2000 BMW 328i, 1996-1999 BMW 328is, 1989-1995 BMW 525i, 1993 BMW 525iT, 1982-1988 BMW 528e, 1997-2000 BMW 528i, 2007-2010 BMW X3, 1997-2000 BMW Z3, and 2007-2010 BMW Z4.
This set includes main bearings for BMW M20, M50, and M52 engine families.
The bearings feature a bimetal construction with an aluminum base.
This is a 0.75mm undersize bearing set, intended for use with a crankshaft machined to this specification.

Secure CheckoutFast Shipping631-982-0042

Will this fit your vehicle?

About this part

Product Details

This is a main bearing set from King Engine Bearings, part number MB798AM0.75. You get the main bearings needed to service the crankshaft journals in a range of BMW engines. These bearings are constructed with a bimetal design, meaning they have an aluminum base for good thermal conductivity and wear resistance.

These bearings are specifically sized at 0.75mm undersize, which is important if your crankshaft has been machined down to this size during a rebuild. King Engine Bearings is a well-known name in engine components, and this set is designed for BMW M20, M50, and M52 series engines. This includes popular models like the BMW 325i, 328i, and 525i, among many others. Proper bearing clearance is critical for oil pressure and engine longevity, and these bearings aim to provide that for your rebuild.