I'm not 100% sure, but I think that the more off road oriented tires also have stiffer sidewalls for this (and other) purposes. I have done some pretty tough rocky trails on my strom with a Mitas E-07 Dakar on the front, hit things very hard, and never bent my rim. I'm surprised you are riding stuff this hard on those tires. I have Shinko 704/705's on my WR and I can't wait to get them off of there. Last year at a single track course with my strom the instructor looked at my E-07s (a 50/50 tire) and called it a street tire.