Using rump steak in a stew, will the meat go tough?

try instead to make your stew sauce but for the meat you want it to be cooked for as low as possible for as slow as possible, i would seal the meat then put it in stock and braise it in the oven but at 90C it must be at least more than 72C which is the minimum safe point to prevent bacterial growth. and i would cook it for 24 hours. it seems crazy but we do this in the restaurant and its really great, although we do have a special machine in order to do that, i (pardon the expression) dumbed it down so that it could be done with conventional equipment.