Seatpost sizing stupidity

My own stupidity, not the manufacturers.

What do the numbers refer to in these item listings? i.e 27.2 - 350L

FSA SLK Carbon 0 deg 27.2*350L Seatpost

FSA SLK Carbon 0 deg 31.6*350L Seatpost

FSA SLK SB20 SBS Carbon Seatpost 27.2

FSA SLK Carbon Seatpost 350mm 27.2

27.2 clamp size
350mm in length

dude, srsly?...seatpost diameter (27.2 / 31.6 etc) and length of post (350mm etc)...

Ah! So most bikes are 27.2?

most not all
what bike you after a post for?

Not sure yet.

Dolan Track Champion, Bianchi Pista Concept, Condor Lavoro or Cinelli Vigorelli or Mash Vigorelli.

But I've got an FSA chainset and there's a good deal on FSA seatposts at Planet X at the moment.

Several bikes in the world are 27.2mm yes.

Read Sheldon and stop askin daft questions

Fuck. I didn't realise there were so many sizes. Better wait til I actually have a frame to attach it to then I suppose.

theres every size you can imagine
so dont buy nothing until you know what frame

you can get shims for a fiver. most modern frames do not go below 27.2 so if you have a 27.2 post you can get a shim that will make it fit to a larger size seat tube.

if you want a negative shim then i think BRM sells them?

ASM bought all his stock a few weeks ago.

Right, fuck it I'm going to buy one. 20 quid for a new carbon seatpost that will match other components and retails around 50 quid normally. It's worth a risk.

@last_caress

if you want a track bike for the track, you can't go wrong with a Dolan Track Champion. For an extra 80 quid they will paint it any colour you want too. Another 100 will get you semi-custom geometry(although the standard geo is perfect) like a sloping (forward) top tube.

bit of a thread hi-jack but does anyone know if there is a standard seatpost size for reynolds 500 tubing? i (wrongly) assumed it was 27.2mm but have since measured and it's 26 ish. is there a regualtion size as in 26.2 26.4 etc?

thanks

gah, I had this problem. using calipers I got every measurement from 26.6 to 27 and 27.2 def. didn't fit. it's a pain.

if you want a negative shim then i think BRM sells them?

A negative shim is called a reamer and costs a lot more than a shim or even seatpost.
(Adjustable) reamers become very handy when you didn't grease trhe seatpost before assembly into the frame and you cannot get it out anymore after 5 years of maintenance-neglicence.

gah, I had this problem. using calipers I got every measurement from 26.6 to 27 and 27.2 def. didn't fit. it's a pain.

ok no worries, i could always hang on to the 27.2 and wait til someone has some reverse shims back in stock.