few years ago a mate rings me up trying to replace rear pads on a rear disc little car,i get there and see its got those wind back pistons,we just fumbled around with pointy pliers and got it done,seeing my wife just got a newer car with rear disc brakes thought Id just buy a cheap "brake cube"you stick a 3/8 drive into it after you select what pattern you need,bit easier if the wind back is stiff,plus i dig weirdo special tools!