How Do Piston Rings Rotate in the Cylinder Bore?

Piston rings rotate in the cylinder bore due to friction caused by engine load.

Piston rings refer to circular, springy metal seals that fit into grooves set in the pistons of an internal combustion engine. Piston rings rotate in the cylinder bore, the internal diameter of the tube in which the piston pumps.

Functions

Piston rings support heat transfer from the piston to the wall of the cylinder, as well as seal the expansion, or combustion chamber. Piston rings also help regulate the engine's oil consumption to enable better engine performance.

Rotation

When the engine operates, it causes vibrations in the cylinder bores.This vibration results in piston rocking, which creates friction generated by uneven ring contact around the circumference of the ring grooves. The rings then spin while moving up and down the length of the cylinder.

Compression

A piston ring that slips out of its groove may cause the combustion mixture to leak between the cylinder and piston. This can lead to engine hesitation and reduced engine performance. Replacing the piston, bearings and any other worn or damaged parts typically restores proper engine function.

References

• Dan's Motorcycle Repair Web Page: Pistons, Cylinders & Rings
• "Car Science"; Richard Hammond; 2008

Resources

• Read this Article in Spanish
• "How to Repair Your Car"; Paul Brand; 2006