an asymmetric damping mechanism for use in a belt tensioner . the damping mechanism comprises two parts having substantially similar arcuate shapes for engaging a tensioner . the first part is in contact with the second part at a pivotable point of contact . the point of contact position is determined according to the desired asymmetric damping factor . the first part is also in contact with a spring . the second part is in contact with a tensioner arm . the damping mechanism also comprises two damping shoes , each having a damping band . the damping band is joined to the damping shoe by a plurality of vertical grooves on the damping shoe cooperating with a plurality of grooves on the damping band . the damping mechanism has an asymmetric damping factor in the range of approximately 1 . 5 to 5 .