Just a question for the collective wisdom of the group. In an application like this, a hardened bolt would be tougher (stay away from stainless steel, not as strong) but, is this application not a good spot for a grade 8 or grade 10.10 (metric) because swith that hardening you also will see it be more brittle? It is a suspension part after all and sheering in failure is often going to really ruin your day in a major way if it occurs at any speed. Much less when at high speed and you hit a pothole you didn't see or have to swerve to avoid something and in doing so have to hit an immoveable object. ( Of course if you do hit something big enough to do a lot of damage to the rear then you probably have also hit it with you front wheel and being a spoked wheel it may not be anything ressembling round any longer and you have far more problems quickly happening than worrying about a broken stud/bolt.... sorry for the run-on sentence...)
I think about the wierdest things sometimes, too much work in risk analysis and risk contingency plans/ stuff over the years in my work.
