When measuring a cylinder, which condition is indicated by reading diameters at the top, middle, and bottom of ring travel?

When measuring a cylinder, which condition is indicated by reading diameters at the top, middle, and bottom of ring travel?

• A. Piston clearance
• B. Cylinder alignment
• C. Cylinder taper
• D. Cylinder out of round

Answer: (C)

Bore taper is a condition where the cylinder bore diameter changes along its length. Measuring diameters at the top, middle, and bottom of ring travel directly checks for this axial change. If the bore gets progressively larger or smaller from top to bottom, that pattern shows taper, often due to wear patterns or manufacturing variation. The rings sweep through the bore along that travel, so sampling at these positions reveals how the bore diameter varies along the cylinder. If it were out of round, you’d see diameter differences around the circumference at a single cross-section rather than a consistent change along the length. If you were assessing piston clearance, you’d focus on the gap between the piston and bore at a specific location, not on how the bore diameter changes along the stroke. Thus, reading top, middle, and bottom diameters indicates cylinder taper.

Bore taper is a condition where the cylinder bore diameter changes along its length. Measuring diameters at the top, middle, and bottom of ring travel directly checks for this axial change. If the bore gets progressively larger or smaller from top to bottom, that pattern shows taper, often due to wear patterns or manufacturing variation. The rings sweep through the bore along that travel, so sampling at these positions reveals how the bore diameter varies along the cylinder. If it were out of round, you’d see diameter differences around the circumference at a single cross-section rather than a consistent change along the length. If you were assessing piston clearance, you’d focus on the gap between the piston and bore at a specific location, not on how the bore diameter changes along the stroke. Thus, reading top, middle, and bottom diameters indicates cylinder taper.