Bearing shells appear to have a larger contact area, so theoretically, the frictional resistance should be greater, and the wear rate should be faster. Why then is such a crucial component as the engine crankshaft used with bearing shells?
Actually, although bearing shells appear to have a large contact area, they are pressure-lubricated. When the engine is running, the oil pump generates high pressure, and oil flows out of the oil holes in the bearing shell at high pressure, filling the space between the crankshaft journal and the bearing shell.
This creates a sufficiently thick oil film on the contact surface, making the crankshaft appear to be "suspended," resulting in very low friction.
