Piston Rings

Piston rings are open ended rings that fit into grooves on the outside of a piston. They are often used for moving pistons, like those of engines. Piston rings help to reduce leakage, with the ring gap compressing when inside the cylinder bore.

Piston Ring Manufacturers

  • Precision Rings: Precision Rings is a leading manufacturer of custom piston rings and seal rings, specializing in piston rings for hard environments or tight tolerences. Precision Rings has 60 years of experience and a dedication to providing their customers with the finest quality rings products and responsive service.

Types of Piston Rings

While piston rings have a number of applications dating back to steam engines, they are most commonly found in automotive engines. There are two primary types of piston rings in vehicle engines: at least two piston rings are required for a piston/cylinder and most engines use three. These two types of piston rings are:

  • Oil Control Rings: this piston ring sits lower on the piston and its purpose is to control the supply of oil needed to lubricate the piston skirt and the compression ring. Automotive engines typically have one oil ring.
  • Compression Rings: this piston ring sits at the top of the piston and while it also helps to control oil, it’s main function is for compression sealing. Automotive engines typically have two compression rings.

Materials and Wear for Piston Rings

Piston rings wear as they travel up and down the cylinder bore, and are often times considered a sacrificial part, protecting the cylinder at their own expense. The wear on piston rings is minimized by manufacture from wear-resistant materials and application of coating to enhance the wear resistance.

Piston rings are typically manufactured from cast iron or steel. Traditionally, cast iron (grey cast iron or ductile iron) was the material used for automotive piston rings. Cast iron is less and less common in automotive piston rings today, with manufacturers increasingly preferring the advantages of steel for piston rings.

Steel offers a greater tensile strength, higher yield strength, significantly improved hardness and a greater fatigue life when compared to cast iron. In addition to these advantages, a steel piston ring has a lower ring mass than iron. The lower mass itself reduces the wear on the piston rings by reducing it’s own load.


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