Originally Posted by
Toddorado
There is an ongoing debate on whether it makes a difference if the weight is on the bike or the rider. I am a backpack guy who recently tried a rear rack and trunk. After a week of huffing and puffing up hills on which I was previously comfortable, I am convinced (at least for me) that when I weigh my bike down, I have a harder time moving it. I hate that I must drive the car on my Monday in order to get appropriate clothes and food to work for the remainder of my week so I don't have to weigh myself down on the trip each day.
Why not try out your theory with a timed commute, one with backpack and the other using the rack/trunk? Fill the thing up, so you can better check the time differential.
I don't think there is a difference between a rack mounted bag or a backpack, both filled with the same weight, on the speed of a cyclist.