This is a Dahon Presto Lite. It's my London bike, because it can fold into rush hour trains. It's under a spoiler so as not to spoil the suspense.
The problemWhen riding this I wear a backpack. It gets heavy because I fill it up. My back suffers.
The solutionDon't fill it up.The solutionOf course I'm going to fill it up. A half empty bag taunts you until you do.
I needed a bag small enough that I wouldn't mind carrying it around, but large enough to be useful; preferably one which attached to the bike. The best bag is also one which goes on and comes off quickly. Who wants to be messing with velcro straps when there are precious seconds at stake? (Folders get you thinking in terms of seconds. Check out the advertising.) Nor did I want to waste bag space on the lock.
The saddlebag I use on my full-size bikes looked ideal. I could have clipped it to the top of the seatpost, but that would have messed with the folder's low centre of gravity. Needing a second seatpost of sorts, I got a pipe from Homebase and had them cut it in different lengths for me to play around with. Then I wedged the pipe into the frame
like so and strapped it tight with jubilee clips.