A large pot hole opened up in the road between Culdrose and Cury Cross Lanes last week as a result of flood water.
The hole was reported to police as being on the A3083 on the Helston-bound road, at the Skyburriowe turning.
It was called in by a member of the public at 5.30pm on Tuesday last week.
The caller described it as being “two and a half foot and expanding,” and filled with water.
A police spokesman said the hole was in the middle of the road and “very hazardous to motorcycles.”
Cornwall Council’s highways department was called to deal with the problem.