Originally Posted by
fietsbob
With A Kalloy Plain seatpost on both bikes and a separate saddle clip, ( Brompton's ($30) Pentaclip is the best)
you can slip the saddle clip off the post top and move It.
yes standard seat post , and frame bores are Increasing in even Increments, 0.2mm at a step , so the 26.5 is likely a measuring error.
USE [UK] precision machines their seat post sizing shims, they made a 25.0 seat post and a 27,2 seat post and sold shim sleeves to use the smaller
seatposts in all the sizes in between.
[ The Shim thickness difference is 1/2 the difference in diameter , 26,4-25,0= 1.4 , so shim stock thickness has to be 0.7mm ]
Might need an accurate digital caliper, they are not that expensive with China making them, too.
You are absolutely right - I have a cheap (from India, not China) vernier caliper that's imprecise. Also, the smaller (I thought 25.0) seat post dates from the '70's and fits my Raleigh frame, also circa 1970. The advantage of fooling with home-made shims is you can find the right fit by trial and error. Once done, it's done. (I do need a better caliper.)
The Kalloy and Brompton products sound like the ideal solution, if I can get the right diameter post(s).