I've got a 27.2 seattube I want to put a suspension seatpost on.
I have a couple 25.4 suspension seatposts plus a a 26.0 that was once sent me instead of the 25.4 I ordered. Thought I'd shim the 26.0 since that seatpost is otherwise unusable on any of my hardtails (all other hardtails are 25.4 or 13/16). Seems since 26.0 is such a rare size, I couldn't find the proper shim. Should just get 25.4 to 27.2 and store the 26.0 boat anchor or is there a source for 26.0 to 27.2?
2003 Specialized Hardrock, 2004 LOOK KG386i, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1
Sorry, I read the description incorrectly. Your interpretation is correct. For some reason why I first read it I thought the seatpost and seattube diameters were adjustable.
Your best bet is to find some shim stock and use it to convert your 26.0 post to 27.2 or whatever you want. .025" (.635mm) thick aluminum is available in 2024 alloy from McMaster Carr for $15 for a 12" x 12" sheet (enough for many failed shim attempts ). It's ever so slightly bigger than what you'd ideally use (0.6mm = .0236") but worst case you'd need to lightly sand it down to get a better fit. It won't be as pretty as a purpose made shim but it should do the trick.
You can get brass sheet from just about any hobby store, but 0.025 (in reality, it's probably 22 gauge, which is 0.0253") might be a touch too thick to fit. The necessary thickness is a bit less, ~0.0236". 24 gauge (0.0201") might work better, since the clamp is made to go smaller than the nominal size, but the seat tube can't get any bigger.