🔍 Key Concepts

• piston motion near TDC (top dead center) and where side thrust is actually greatest in the stroke • what causes ring and cylinder wear: pressure, temperature, and contact between rings and liner • how gas pressure on the compression rings changes as the piston approaches and leaves TDC

💭 Think About

• At what point in the stroke is piston side thrust usually greatest: near mid-stroke or exactly at TDC? How does that affect option A? • Does the piston skirt have its greatest contact at the very top of the bore, or lower down where the piston is better guided? How does that relate to option B? • Near TDC during firing, what happens to combustion pressure around the top ring belt, and how would that influence wear compared to acceleration effects in option D?

✅ Before You Answer

• Identify where the combustion pressure peak occurs relative to TDC and how it loads the compression rings against the liner near the top of the bore • Recall that piston acceleration is zero at exact TDC and BDC, not maximum there; check how that affects option D • Consider where the ring reversal area is (where rings change direction) and why that region near the top of the stroke tends to experience more wear