More than everyday biking stuff. I load my carradice camper longflap up with my 2 weeks of grocery shopping which tops 30 pounds, and no problems with the brooks yet. Admittedly, the ride to the grocery store is about 1/10 of what most folks will do in a day of touring, but nonetheless.. I plan to use only the saddlebag and a small handlebar bag for a 3 week trip I am going on next month. If I needed to move some rocks around, I would certainly not hesitate to toss them in the bag too, although it seems that the folks at brooks advise against it.