What does a ring compressor do?

A ring compressor is a tool specifically designed to compress piston rings, allowing them to fit snugly into the cylinder walls when installing a piston into a cylinder. This compression minimizes the overall diameter of the rings, making it easier to insert the piston assembly into the cylinder without damaging the rings or the cylinder walls. Proper installation of piston rings is crucial for engine performance, as it ensures an effective seal within the combustion chamber.

While the other options mention aspects of piston ring handling, they do not accurately describe the primary function of a ring compressor. It does not expand the rings for installation or align them during assembly; rather, its main role is to reduce the size of the rings for a smooth and safe installation process. Removing piston rings from an engine is also not the job of a ring compressor—it focuses exclusively on the installation phase. This makes the choice highlighting the compression of piston rings the most accurate.