What explains why the advancing speed and the retracting speed are different on a double acting cylinder?

The advancing speed and the retracting speed of a double acting cylinder can vary due to the geometric differences in the areas being acted upon by the hydraulic fluid. When a cylinder extends, the fluid exerts force on the entire cylinder area, which includes the area of the piston. However, during retraction, the area on the rod side is diminished because the rod occupies some of the volume of the cylinder.

This reduction in effective area results in a smaller volume of fluid being required to move the piston back into its housing compared to the volume required to move it outward. Consequently, despite similar pressures, the flow rate and thus the speeds of advancing and retracting can differ. The larger volume of fluid needed when the entire piston area is utilized during extension means it will usually extend faster than it retracts.

The choice that accurately captures this situation is the one stating that the cylinder volume on the side with the piston rod is smaller, as it highlights the basic principle that affects the operation of the double acting cylinder.