Looking for a replacement seatpost and want to match existing layback. How is it measured? From centre of post to somewhere? or front of post to somewhere?
Well I've got a 12 incher but I don't use it as a rule.
Base to tip.
AFAIK it's centreline of shaft to centre of rail clamp.
The manufacturer will tell you one thing, but it'll be different to what it actually measures, so the only way to know for sure is buy a load of seatposts and measure them yourself.
AFAIK it’s centreline of shaft to centre of rail clamp.
It's normally this ^
But sometimes It's not, and even when it is you then have to take into account how big the clamp is, one post with a deep/long clamp and layback Xmm might not let you get the saddle in the same position as another post with the same measured layback but a narrower clamp if your saddle has short rails or is at extreme of adjustment
From the hinge end