🔍 Key Concepts

• thermal expansion of metal piston rings as temperature increases • purpose of the cold ring end gap specified by the manufacturer • what happens when ring ends butt together instead of keeping a clearance

💭 Think About

• Think about what happens to the length of a metal ring when the engine reaches full operating temperature compared with when it is cold. • If the cold end gap is made too small, what will the gap look like when the ring gets hot and expands? Will there still be clearance, or will something change at the ring ends? • Once the ring ends lose their clearance, what kind of mechanical stress or deformation could occur as the ring is forced against the cylinder wall?

✅ Before You Answer

• Verify which option best matches a condition where the ring over-expands and the ends touch or force against each other. • Eliminate choices that describe problems more related to too much clearance (excessive gap or side play) rather than insufficient end gap. • Consider which failure mode would most likely result from binding due to heat expansion rather than contamination or slow wear.