Pistons are used in internal combustion (IC) engines, compressors, pumps, and other machinery items. Pistons are contained within a cylinder and travel linearly between top dead centre (TDC) and bottom dead centre (BDC). Pistons are commonly made of aluminium or cast-iron alloys.

Piston rings are used to seal the space between the piston and cylinder (to be specific, it is actually a thin film of lubrication oil between the piston rings and cylinder that performs the sealing).


Generally, a small two stroke engine will have two piston rings and a four-stroke engine three. It is possible for one ring to have multiple roles e.g. wiper and oiler.

Piston Assembly  

Piston Assembly

Piston Components

Piston Crown

Due to its location, the piston crown encounters significant pressures and temperatures. The design of the crown varies considerably, as many crowns have a unique topography to distribute the exhaust gasses created by the combustion process.

Piston Ring Groove

The piston rings are located in the piston ring grooves

Piston Pin Support

Piston pin supports are used to spread the pressure over a larger contact surface area, this reduces the probability of piston cracking/failure.

Piston Skirt

The type of skirt shown here is a ‘full’ skirt.

Hole for Piston Pin

The piston pin slides into this hole. The pin connects the piston rod to the piston.

Piston Interior

Oil is circulated inside the piston head to remove the heat generated during the combustion process.

Piston Pin Cover

Sometimes a cover will be used to seal the piston pin. C-clips are used to hold the seal in position.

Piston Skirt Reinforcement

Additional reinforcement/support reduces the probability of failure due to cracking.

Additional Resources

Encyclopedia - saVRee