I usually ride with just one pannier, on the left side, carrying a 15" mbp, lunch, clothes, first aid kit, u and cable locks, ski goggles, gloves and hat (at least now that I'm not wearing them and until it's nice enough to forgo them), rain jacket... it's probably 20-25lbs loaded and although it's pretty unstable when I'm walking the bike down the hall, it doesn't even feel like it's pulling when I'm riding. But my rack has a 55lb weight limit and my bike has big cushy tires so YMMV