I'm a back pack guy, too. I carry 4 tubes (2 each for my 2 different-size wheel commuter bikes) pump, multi-tool, plus a change of clothes or whatever else I need for the day. I just sling it on my back and I'm good to go with no worries about changing gear over from one bike or bag to the other. It's just easier for me to remember this way. If I'm going over 50 miles, I might modify my carrying scheme, especially if I am riding my bike that has panniers. I will admit that those rare rides I take with no weight on my shoulders feel like I am flying! Or cheating.