Rusted nuts, the lock ring will not come off until you knock the tire down. You will either need a large tire hammer like this http://www.bigdogtoolz.com/kn35429.html or a slide hammer like this http://www.bigdogtoolz.com/kn35429.html I prefer a hammer. Put plenty of rubber lubricant such as Ruglyde or soapy water on the bead. Once you get the bead knocked down an inch or so, you can pry the lock ring off with one of these http://www.keenzo.com/showproduct.asp?M=KEN-TOOL&ID=1433144&ref=GB.