Front derailleur wide range
I am trying to set up a 16" folding bike with a wide range front derailleur. My preference would be a double with 26-53, or 28-53 the lower the better it has capreo in back so limited to 26 largest rear. My question is will any front der do the 26-53 or 26-50. I have the proper spiders and rings to mix and match. Also would it shift better it if was a triple with a 39T middle? I prefer double just for weight saving and easier to adjust but will do a triple if needed. Sheldon Brown has a pic of a double with a tiny low and a huge high but no info on the model FD. He is a bit hard to reach in bicycle heaven with all downhills and tailwinds. I have figured all the gear inches and ratios just a question of workability. 2nd question, the best place to attach the shifter would be quite close to the FD on the seatstay. Will a very short FD cable length make it not work well? I am going to use a friction shifter.Thank you I guess the hard thing for me to find is a FD with a range of 25 to 27 teeth and can handle a 53
If you are using a barend or other friction shifter for the front derailleur you should be ok with the wide range double. Shifting from the 26 to the 52 or 53 won't be super fast but it will be adequate. You will certainly want to fit a chain watcher to prevent the chain from dropping to the inside during downshifts.
You want a road front derailleur intended for a triple crank since the cage is longer and that keeps the chain from dragging on the tail of the cage in the small chainring. I have both Campy and Shimano triple front derailleurs used with 53/42/26 and 52/42/26 cranks and these handle that range of chainrings with no problems.