he can't he doesn't have a hanger... you don't get perfect tension, when you spin your cranks the chain will bob up and down, cause the drivetrain isn't perfect, you need to spin the cranks, find the tightest point and then adjust the tension around this point. the tugs on the zoot are aweful, i ruined mine in a week, you need to go to an old bikeshop in the hopes that they sell some big gnarly chain tugs, cause aluminium ones just never seem to cut it