MAHLE 4025MS-15 Piston Ring Set Bore File Fit - 4.020 005 1.5/1.5/3.0mm

The MAHLE 4025MS-15 is a performance piston ring set designed for a 4.020" bore (+.005" oversize) with a file fit configuration and standard tension. Ring groove sizes are 1.5mm / 1.5mm / 3.0mm, making this set compatible with metric-groove pistons commonly used in high-performance and racing engine builds.

MAHLE pioneered the use of piston ring simulation and computer-aided development tools to engineer rings that deliver measurable horsepower gains by minimizing friction. The results are proven on the dynamometer and on the track. MAHLE's ultra-flat ring flanks maximize ring-to-piston groove sealing for improved compression retention and reduced blowby.

Ring Construction:

• Top Ring: Ductile iron construction with plasma moly coating and a barrel face profile for superior sealing and break-in characteristics
• Second Ring: Cast iron with a reverse twist design to improve oil control and sealing efficiency
• Oil Ring: 3-piece standard tension assembly providing reliable oil control across a wide range of operating conditions

Key Specifications:

• Bore Size: 4.020" (+.005" oversize)
• Ring Widths: 1.5mm (top) / 1.5mm (second) / 3.0mm (oil)
• Fit Type: File fit for custom end-gap tuning
• Tension: Standard
• Top Ring Material: Ductile iron, plasma moly, barrel face
• Second Ring Material: Cast iron, reverse twist
• Oil Ring Style: 3-piece

File fit rings allow the builder to precisely set the ring end gap for the specific application, making this set ideal for performance engine builds where accurate tolerances are critical. MAHLE also offers this ring family in 1/16", 1/16", 3/16" imperial sizes as well as ultra-low friction .043"/.043"/3.0mm configurations for specialized racing applications.