I'm hoping for some advice on changing out the handlepost and handlebar on my Dahon Boardwalk. It is an older Boardwalk, bought several years ago. It has a seven-speed rear derailleur with a twist-grip shifter. The handlepost does not telescope, the handlebar clamp does not flip open (it has a quick-release that allows the bar to be rotated, a pin in the clamp portion of the handlebar fits in a slot in the clamp to keep the bar centered), and after unfolding you have to rotate the safety catch. I hope that helps identify it.
The goal is to get a lower and more forward handlebar position.
My tentative plan is to buy a Jetstream handlepost from Thor USA, like this one
Handlebars, Extenders and Bar Ends
and install a bullhorn handlebar.
My questions are:
1. Will this handlepost fit on my Dahon?
2. Can I clamp the bullhorn bar directly into the flip-open clamp of the handlepost, or will I have to buy a "stem"?
3. If I do have to buy a stem, is there one with about 80-100 mm length?
4. Is there an integrated shift-brake lever that is pretty cheap (like Tiagra/Sora cheap), and will work with this derailleur? Either new, or something I can find used on eBay?