| Ive snaped the center bolt off once but its easy to get out. this would work if you cant get a grip on it with vice grips too. You can get a rheemer (I think its called that) like a reverse drill bit. You just drill a hole in the bolt then jam it in and reverse drilll it out. It should just unscrew out. Drilling the hole weakens the bolt too and makes it come out easily. | 
