I have a 2002 Dahon boardwalk S1 and I was wondering if anybody knew the diameter of the seat tube to install a front derailleur. Here is a factory picture of the style I have.

Why do you want a front derailleur? I would use my HF caliper to do what you want and available for a couple of dollars. I have 2 S6 now S7 Boardwalks and would not add a front derailleur to them. Roger

Are you away from the bike, so that you cannot measure it? Otherwise, if you have no caliper at hand, you can measure circumference with tape, and divide by Pi. If you have no tape, use a string and then measure the length of the string representing the circumference with a ruler. The general problem with Dahon is that they can market bikes that differ in details under one name, i.e. if you ask somebody else for measurements, you may slip. Of course checking the appearance helps.

Ok, I'll measure it tomorrow. I just thought they were all the same standardized size.

the seattube is 39.9 mm

Thx for info. I was picked up a 7x3 Sachs hub that might work out better. Just have to find compatible shifters.

take care with hub shifters that they cable travel are wacky and uneven in eatch step.
a wrong shifter may destroy the hub.

I decided to go with a 52 single front and a 9 speed rear. Still have shifter and brakes cables to install and adjust. Plan on having it rideable tomorrow.

great!

for you as a boardwalk owner check out this website for extensive mods and howtos in this model.
https://handsonbike.blogspot.com/p/d...x20-r.html?m=1

Love that blog! Thanks for bringing it to the thread!

Nice bike and good build but you never explained why a front derailleur measurement. Roger

I was thinking of adding a triple chainring but changed by mind.

Something I’ve noticed about the Boardwalk folders is they are similar to the Mariner bikes. Mariners are multi-geared though.

You converted your bike from a single speed coaster hub to a 9 speed? what parts and where did you buy them?