Originally Posted by fietsbob

Tool: Adjustable hand reamer ..+ patience.. take more time .. I did this .. taking Out 0.1mm wall thickness
to go from 27.0>27.2 so new seat post, already in hand, before starting the job, just slipped in .. RB1 frame

only turned the cutter adjustment out like .01mm at a time, so as to not cut too much, and the chips stuck in the cutting oil
which was wiped off the tool and re applied oil repeatedly ..


By the way Bromptons Pentaclip is great Its a stepless saddle clip of aluminum [5 main parts ..penta, get it. ?]

problem with low cost seatposts is usually the head they put on them.. A Straight Kalloy post itself is adequate.

and there are 25.0 posts , like USE with springs+ elastomers . they sold shims to 27.2,
then the next one made was 27,2 then shims for frames bigger than that as well

I have a thudbuster seat post in a 31.4 frame post is 27.2..

25.4 is another common shim ID..