What does '0.25mm undersize' mean for these bearings?

This means the bearings are designed to fit a crankshaft that has been machined down by 0.25mm. This is a common practice during engine rebuilds to ensure proper fit and oil clearance on a worn or resurfaced crankshaft.

What is the construction of these main bearings?

These bearings are made with a bimetal construction, which uses an aluminum base. This type of construction is chosen for its performance characteristics in supporting the crankshaft.

Do I need to replace my crankshaft when using these bearings?

If your crankshaft has been worn beyond its standard tolerance or has been resurfaced, it will likely need to be machined to an undersize dimension, such as the 0.25mm for this bearing set. Always check your engine's service manual for specific machining and clearance requirements.

Specifications

Brand: King Engine Bearings
Part #: MB580AM1.25
UPC: 611500172854

King Engine Bearings Toyota 21R/(Size +0.25mm) Main Bearing Set

Name: King Engine Bearings Toyota 21R/(Size +0.25mm) Main Bearing Set
Brand: King Engine Bearings
SKU: king-engine-bearings-king-engine-bearings-toyota-21r-size-0-25mm-main-bearing-se-t14-770987
Price: 50.69 USD
Availability: BackOrder

$50.69

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Fits 1975-1990 Toyota Pickup. King Engine Bearings main bearing set, 0.25mm undersize, for 21R engines. Essential for engine rebuilds.

Key Features

Fits 1975-1990 Toyota Pickup, 1975-1983 Toyota Celica, 1975-1982 Toyota Corona, and 1984 Toyota 4Runner.
Designed for Toyota 21R engines.
Main bearing set is 0.25mm undersize, for use with a machined crankshaft.
Features a bimetal construction with an aluminum base.

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About this part

Product Details

If you're rebuilding the engine in your 1975-1990 Toyota Pickup, especially one with the 21R engine, a fresh set of main bearings is crucial. These bearings sit between the crankshaft and the engine block, supporting the rotating assembly and ensuring smooth operation. This set from King Engine Bearings is built with a bimetal construction, using an aluminum base for good performance characteristics.

This particular set is sized at 0.25mm undersize, meaning it's intended for a crankshaft that has been machined down by that amount during an engine rebuild. Using the correct bearing size is vital for maintaining proper oil clearance, which is key to engine longevity and performance. King Engine Bearings is a well-known name in engine components, and this set is a solid option for your engine project.