What does '.25mm undersize' mean for these main bearings?

This means the bearings are manufactured to be 0.25mm smaller in diameter than standard. They are intended for use when the crankshaft journals have been machined down by 0.25mm to ensure the correct oil clearance and fit.

Do these bearings come with installation hardware?

This listing is for the main bearing set only. Installation hardware, such as main cap bolts, is typically sold separately. Always refer to the manufacturer's service manual for a complete list of required parts and procedures.

What is the warranty on these ACL bearings?

ACL typically offers a limited warranty on their engine bearings against manufacturing defects. Please consult the ACL warranty documentation or contact our customer service for specific details regarding this part number.

Specifications

Brand: ACL
Part #: 7M1512H-.25
UPC: 9315726470091

ACL BMW B58B30/S58B30 3.0L Inline 6 .25mm Oversized Main Bearings

Name: ACL BMW B58B30/S58B30 3.0L Inline 6 .25mm Oversized Main Bearings
Brand: ACL
SKU: acl-acl-bmw-b58b30-s58b30-3-0l-inline-6-25mm-oversized-main-bearings-t14-719895
Price: 300.07 USD
Availability: BackOrder

$300.07

On Backorder

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

Fits 2016-2018 BMW 340i. ACL .25mm Oversized Main Bearings for B58B30, S58B30 3.0L Inline 6 engines.

Key Features

Fits 2016-2018 BMW 340i, 2018-2019 BMW X3, and 2020 Toyota GR Supra.
Designed for BMW B58B30 and S58B30 3.0L Inline 6 engines.
Main bearing set is .25mm (0.010 inches) undersize for use with machined crankshafts.
Well-built by ACL, a trusted name in engine components.
Crucial for restoring proper oil clearance during engine rebuilds.

Secure CheckoutFast Shipping631-982-0042

About this part

Product Details

Doing an engine rebuild on your BMW 340i, X3, or Toyota GR Supra with the B58B30 or S58B30 engine? These main bearings from ACL are a solid option for ensuring proper crankshaft support. Main bearings sit between the crankshaft and the engine block, handling the immense forces generated during combustion and rotation. When rebuilding or repairing an engine, especially one that's seen high mileage or performance use, replacing these bearings is a critical step to restoring oil clearance and ensuring long-term reliability.

ACL has been making engine bearings for a long time, and these are well-built for the job. This set is specifically .25mm (0.010 inches) undersize, meaning they are intended for use when the crankshaft journals have been machined down to match this size during an engine rebuild. This precise sizing is crucial for maintaining the correct oil film thickness, which is vital for lubrication and preventing metal-on-metal contact. The material and construction are designed to handle the loads and temperatures found in these performance inline-6 engines.

When you're deep into an engine build, getting the bearing clearances right is paramount. Make sure you have your crankshaft measured and machined to the correct .25mm undersize before installing these bearings. Always refer to the manufacturer's service manual for the specific torque specifications and assembly procedures for your engine.