Bearing Materials

As discussed earlier, there are three basic types of engine bearings—connecting rod bearings, crankshaft main bearings, and camshaft bearings. The backing material (body of the bearing that contacts stationary parts) for engine bearings is normally steel. Softer alloys are bonded over the backing to form the bearing surface. Any one of three basic types of metal alloys can be plated over the top of the steel backing—Babbitt (lead-tin alloy), copper, or aluminum (fig. 3-73). These three metals may be used in different combinations to design bearings for either light-, medium-, or heavy-duty applications. The engine designer selects the combination of ingredients that will best suit the engine.