hey i have some experience of bikes and am hugely stuck i am trying to fix my brakes ill go though how i do this i have side mount calipar brakes i grip them hard and press them to the rim then i tighten the cable with some pilers and then i screw the nut down fixing it in place but when i press the brake lever the cable instantly slackens and the lever jsut jams down and does not spring back i cant understand why this is happening can anyone help me