Piston and piston ring

A piston comprising:

• a piston body with at least one annular piston ring groove in the piston body, said groove having two radially extending walls and an axially extending wall;
• a main piston ring received in said piston ring groove, said main ring having an outer generally axially extending face for sealing engagement with an associated cylinder wall and having an inner generally axially extending face;
• said main ring having a recess opening into said inner face, said recess extending in an outwardly direction toward said outer face;
• and
• an annular auxiliary sealing ring having radially inner and outer ends defining the peripheral boundaries of said sealing ring, said sealing ring being in constant but pivotable gripping contact at its radially inner end with said axially extending wall of said annular piston ring groove such that said sealing ring is able to tilt in the axial direction to either side of the gripping contact location by axially pivoting about the gripping contact location of its radially inner end, the radially outer end of said sealing ring extending into said recess in said inner face of said main ring;
• the arrangement being such that said auxiliary sealing ring does not physically limit the movement of said main ring in said annular piston ring groove.