Quote Originally Posted by 2010AveoLT View Post
it really depends on the Quality of the wrenches you are using: a cheap Chinese made Wrench Set will easily stretch open and will start rounding off any nut or Bolt you use on it (use a better quality wrench set like Craftsman, Kobalt, or any of the REALLY High End Companies like Mac, Matco, Snap-On, or Cornwell.). my advice is to use a pair of Small Vise Grips to grip the 15mm nut to keep it stationary so you can get the 17mm nut off. if you are outright replacing the end links, be as rough as you want as long as you don't damage the Sway bar itself, or the Lower Control Arm.
Quality of the wrench has nothing to do with this specific situation. The OP is completely correct in saying the backing "nut" is very poorly designed. If the outside nut is rusted solid in place, it's difficult to imagine any non-heated technique that will free it up. A Vise Grip will shred this thing and reduce it to metal shards in a heartbeat. Here is a post (#17} from work I did just a few days ago, doing this same job. Another guy posted about some magic elixir that is supposed to loosen anything, but he didn't reply to say if it worked on this particular situation.
http://www.aveoforum.com/forum/f85/r...65/index2.html