ONLY THE TENSION OF THE BELT PUSHING AGAINST IT ,IT JUST SITS THERE AND ROLLS KEEPING THE BELT FROM FLAPPING AND MAKING NOISE ,THE TENSIONER DOES HAVE TENSION AGAINST THE BELT , IT IS A SPRING LOADED TENSIONER THAT ALLSO HAS A SMALL HYDRAULIC PISTON IN THE HOUSING WHICH IS WHAT USUALLY FAILS , THIS ONES PUSHES AGAINST THE BELT JERRY