A vertical impact motion of piston ring in the ring groove causes the collision and mutual friction between the surface of piston ring groove and piston ring side, where the first ring groove is most serious and easing off downwards, in some times, some abnormal causes may result in the abnormal wearing of piston ring groove and piston ring. Main reasons involve:

1. The piston ring is fluttered during the motion for some reason.

2. The excess coke in the first ring groove results in the wearing of ring groove side.

3. The inferior lubrication of piston ring and ring groove members results in adhesive wearing because of the contact between both metals.

4. Excess coke arisng from bad combustion result in ring adhesion, hence that the opening of piston ring is vertically fluttered and result in serious wearing of piston ring opening.

5. The materials of piston ring is unqualified, loosely organized or under low hardness.

6. Void filters (air, fuel and oil filters) causes the entrance of dust and other strange matter into the cylinder, and result in abrasive wear in piston ring groove, especially in the first ring groove.

7. Owing to the breakage of piston ring, the local part of ring groove may be worn and widened.