A tensioner for tensioning a belt includes a support housing that defines, at least in part, a spring cavity and an arm pivotably attached to the support housing. A spring is disposed in the spring cavity and is operatively connected to the arm and support housing to bias the arm to pivot relative to the support housing. The spring is a round wire coil spring having an unloaded axial height and wherein the spring cavity has a height greater than the unloaded axial height of the spring.