You can buy a locking nut removal tool,when for example you lose your special coded socket,got mine from sealey I think,a couple of years ago,about £20,you get 4 or 5 special sockets of various sizes that grip the offending nut and remove it,depends how bad yours is broken and if the socket would get hold of the broken stud,have heard of people welding a nut to the stud and getting a socket onto it that way but it would have to be a good weld,or try and drill the head off of the offending nut,maybe tough to do if the stud is hardened steel ,be careful and dont damage the alloy wheel though,good luck.
wickham
April 2010