I am looking to improve the stem setup of my girlfriend Dahon Speed (200?).

Last year, i installed a 28.6 aluminum tubing with a 100mm ahead stem in place of the T stem/handlebar on her Speed. The riding position is perfect but folding is not great.

It seem the Speed TR 2003 was using an adjustable stem like:
https://www.foldsoc.co.uk/speedtr.html

The adjustable stem could be adjusted straight up for normal folding or down for more reach.

Do you know what size is this stem I mean is it a 25.4 size? If so, is the 2003 Speed TR stem extension inside diameter 25.4 instead of 28.6 or is it a 28.6 inside diameter with a shim?

Do you know which brand of adjustable stem is it?

Thanks for helping!

I think this is the one you mean. https://airportshoppe.com/bikes/microadjust_stem.html

I bought one of these as an upgrade for my 2004 Speed P8, but not from this dealer. No shim was required. You need a 5 mm allen to adjust the angle, and it has an expander wedge which needs to be loosened to adjust the height. I can't guarantee which model years it will work with, but I suspect that it will be okay for most adjustable height stems from recent years. This part is not used on any 2005 or 2006 Dahon models that I'm aware of, so you might want to check that there's actual stock before ordering.

Then the quill is 25.4mm without shim and insert into your stem. The inside diameter of your stem is roughly 25.4-26mm. Mine is 28,6-29mm so i would need a shim. I will need to test it with a similar sized stem i have on hand before buying the right adjustable stem.

Thanks. I am on my way of finding a workable solution!