Which of the following statements about piston rings and cylinder finishes is true?

Which of the following statements about piston rings and cylinder finishes is true?

• A. Cast iron rings may be used in chrome-plated cylinders; chrome-plated rings may be used in plain steel cylinders
• B. Cast iron rings may be used in chrome-plated cylinders; chrome-plated rings may be used in chrome-plated cylinders
• C. Chrome-plated rings may be used in plain steel cylinders; cast iron rings may be used in plain steel cylinders
• D. Cast iron rings may be used in plain steel cylinders; chrome-plated rings may be used in chrome-plated cylinders

Answer: (A)

Piston rings and cylinder finishes must work together for a good seal, controlled wear, and proper oil control. A chrome-plated bore is very hard and smooth, which keeps wear down but can make it harder for rings to seat evenly during break-in. Cast iron rings are softer and can conform to the bore surface as they wear in, forming a reliable seal without excessively scratching or scoring the chrome finish. That makes cast iron rings in a chrome-plated cylinder a sensible pairing. In plain steel bores, chrome-plated rings offer excellent wear resistance and can maintain a stable seal over time, so using chrome-plated rings with a plain steel bore is also a practical choice. Other combinations are less favorable because they either push too hard against a very hard surface or fail to take advantage of the bore’s wear characteristics, potentially compromising sealing or increasing wear.

Piston rings and cylinder finishes must work together for a good seal, controlled wear, and proper oil control. A chrome-plated bore is very hard and smooth, which keeps wear down but can make it harder for rings to seat evenly during break-in. Cast iron rings are softer and can conform to the bore surface as they wear in, forming a reliable seal without excessively scratching or scoring the chrome finish. That makes cast iron rings in a chrome-plated cylinder a sensible pairing.

In plain steel bores, chrome-plated rings offer excellent wear resistance and can maintain a stable seal over time, so using chrome-plated rings with a plain steel bore is also a practical choice.

Other combinations are less favorable because they either push too hard against a very hard surface or fail to take advantage of the bore’s wear characteristics, potentially compromising sealing or increasing wear.