Something to look at as mentioned above is the bushing in the tensioner arm. Mine was wore out causing the two idlers to rub and the belt to ride funky. I also notice that once fixed the belt hit the flat edge of the tensioner pulley but moved to the middle once running. I have run both 1/2 and 5/8 belts this year with the wider belt running better. I know many mention 9/16 wide belts but the case cross reference book lists 1/2 wide. The 1/2 wide I have ran good for and our then started twisting. These are tractor supply Kevlar belts.