What Do Big and Small Bushings Refer To?
2 Answers
Automotive big and small bushings are actually bearing shells, divided into crankshaft bushings and connecting rod bushings. They are made of high-hardness wear-resistant steel and consist of upper and lower halves, attached to the connection points between the crankshaft and the engine block, as well as between the connecting rod and the crankshaft. The small bushings are the bearing shells for the connecting rod journal. Since the connecting rod journal is relatively thin, the bushings are also smaller, hence referred to as small bushings. In fact, the engine's crankshaft uses a sliding friction structure, where the crankshaft and the bushings directly rub and slide against each other during rotation. Expansion: The key part of the big and small bushings is the contact surface, which is coated with a wear-resistant material. The coating on the big and small bushings is not a high-hardness material but rather a material that can be easily scratched with a fingernail. Its precision ensures almost 100% contact with the crankshaft. Regardless of whether the engine is running at high or low speeds, it remains stable without shaking, thanks to the indispensable role of the bushings.
I've been driving for over a decade and am particularly familiar with the terms 'big pad' and 'small pad,' which are quite common among car enthusiasts. The 'big pad' refers to the brake disc, that large metal disc next to the wheel hub that rotates with the wheel. The 'small pad' is the brake pad, those small friction material pieces clamped in the caliper. When you press the brake, hydraulic pressure pushes the small pad against the big pad, slowing the vehicle through friction—same principle as bicycle brakes. Both need regular checks: small pads wear out faster, typically thinning after 20,000-30,000 km and needing replacement; big pads last longer but require replacement if deep grooves form. Neglecting them leads to screeching brakes, longer stopping distances, and increased danger in rain. During every maintenance check, I always ask the mechanic to check their thickness to avoid issues on the road.
