Hi all, I recently acquired a hand-me-down folding bike with a missing seatpost n saddle. The brand is Compact. Labels on the frame say 'patented Dahon technology' and '4130 chromoly tubing'. With a caliper I measured the seatube opening with the nylon sleeve in place and it comes to just over 33.2. I plan to try a standard 33.9 dahon seatpost but before I buy, is there any folding bike out there that uses a seatpost diameter close to, but not exactly 33.9?

Yes I've loosened the seat tube clamp all the way. And the opening seems more or less round and not deformed, if the nylon sleeve itself can be used as a gauge. Looking at the slit of the nylon sleeve, the seat tube seems to open up slightly further down than at the opening.

Any insight is much appreciated!

[math quiz]
1.25 " is 31.75 mm. so what is 33.9mm in its inch fractional equivalent?