A belt tensioner for tensioning a belt for a motor vehicle comprises a pivot shaft, a pivoting structure mounted for pivotal movement on the pivot shaft, and a pulley mounted for rotation on the pivoting structure. A spring biases the pivoting structure in a direction that moves the pulley mounted on the pivoting structure into tensioning engagement with the belt. A bolt is constructed and arranged to mount the belt tensioner on the motor vehicle engine mount. The bolt is constructed and arranged to be tightened to a predetermined extent for installing the tensioner of the motor vehicle, the predetermined extent is the same extent to which the bolt is tightened during normal operation of the tensioner. A clamping structure applies a predetermined clamping force on the pivot shaft after the bolt is tightened to the predetermined extent. The predetermined clamping force is sufficiently large to maintain the pivot shaft in perpendicular relation to the engine mount and prevent tilting of the pivot shaft when the tensioner is moved into installed tensioning engagement with the belt, yet sufficiently small to permit manual movement of the pivot shaft relative to the mounting bolt for adjusting the amount of tension applied by the tensioner to the belt.