Where do big end bearings fit?

• A. Around the crankpins at the outer end of each throw.
• B. Between the piston rings.
• C. On the valve stems.
• D. At the center of the crankshaft.

Answer: (A)

Big end bearings are the bearings that support the connecting rod on the crankshaft, allowing the rod to pivot as the crank rotates. They fit around the crankpins at the outer end of each throw, wrapping around the crankpin to form the joint between the rod and the crankshaft. This is how the reciprocating motion of the piston is converted into rotational motion of the crankshaft.

They aren’t between piston rings—that space on the piston is for sealing rings. They aren’t on the valve stems, which have different guiding components. And they aren’t at the center of the crankshaft, where the main bearings sit; those support the shaft itself, while big-end bearings connect the rod to the crankpin.