How is a seatpost measured 22 or 25 ?

[monkeybat]

Is it accross the hole ?

[firebird]

The post will be 22.2mm
 

[monkeybat]

But why have i seen 25 as well?

[firebird]

old school frames take a 22.2 that all I know without making a fool of myself 

[snav69]

But why have i seen 25 as well?

Think that's the Burner size 

 

[spesh]

old school is 22.2mm and then the mid school frames went up to 25.4mm
i think mk1 burners were even bigger 27+ mm?

[monkeybat]

Had to ask as my Mirra flair has a set post but where it gets to the seat it decreases in size and these new micro pivot posts? whats that all about.

[TwoBobRob]

Basically, there were 2 seat post sizes generally used - 22.2mm and 25.4mm, or 7/8" & 1" in old money. It's the actual size of the seat tube hole, and the post of course. Your Haro I'm guessing had a 25.4 post and ordinary looking seatguts and they were always 22.2mm, so the post narrowed at the top.

Most all new school frames take a 25.4 post these days.

The micro pivotal things are just for kids to slam their seats as low as possible.  Some people don't like the position of the pivotal seats as most have no front/back adjustment, so check into that before you buy one if you're thinking of one.

[Jon The Bassist]

Yup, some old Haros were 25.4mm 

[monkeybat]

Measured accross the whole and all mine are 25.4, cheers.

[HARORIDER]

be carefull to check though as there are some odd sizes out there as well like 22.6mm

[spesh]

be carefull to check though as there are some odd sizes out there as well like 22.6mm

my old haro bashguard had a 22.6 post in it

[moochalargo]

Mine field. Glad mine is simple. 22.2