What grade bolts do Thule and Yakima use? I'm surprised to hear this. I haven't looked at the grade codes on the carriage bolts of my Saris equipment, but I've put a 45-lb tandem on mine, and it's held fast. The only bolt I've broken is from a bracket that I bought (very) used. It must have been left on the vehicle in the elements, because the bolt was hopelessly rusted. Two VERY large wrenches later, and of course, I broke the bolt, but other than sawing through it, that was my only choice. For that matter, that might not have been an original bolt.