MAHLE 42155CP.040 Engine Piston Ring Set - 0.040" Overbore

The MAHLE 42155CP.040 is a premium OE-quality engine piston ring set engineered for 0.040" overbore applications. As one of the world's largest original equipment piston ring manufacturers, MAHLE designs these rings to meet or exceed OEM form, fit, and function standards — making them a trusted choice for professional engine builders and rebuilders alike.

These rings are built on an SAE 9254 high-alloy steel base material, delivering superior tensile strength, improved yield strength, extended fatigue resistance, and increased material hardness compared to standard ring stock. Ring materials, coatings, and tension levels are optimized for reduced friction, improved sealing, and extended service life.

Key Features:

• Pre-lapped finish seats immediately upon installation, virtually eliminating traditional break-in time
• Barrel-faced compression ring contact area promotes efficient compression and reduces blow-by
• CNC-controlled gap chamfer on compression rings optimizes sealing and minimizes combustion gas leakage
• Reverse-twist intermediate rings with taper race machining provide better groove side sealing and enhanced cylinder wall contact
• CP-20 oil ring assembly features an exclusive 20-degree ear angle for superior side sealing against the cylinder wall
• Chemically polished oil ring expander enhances oil drain-back performance
• 0.040" overbore sizing for use in engines bored 0.040" over standard bore diameter
• Sold as a complete piston ring set

MAHLE's extensive OE development heritage — including narrow compression rings, low-tension oil rings, and coated ring technology — is built into every set. The 42155CP.040 delivers the reliability and precision engine professionals have come to expect from the MAHLE Original line.