Saddle post offset

shiznit76 wrote:

Hi, I have seen a saddle post I am wanting but it comes with a 5mm or 20mm Offset, what does this actually mean?

Thanks

If you draw a line up the centre line of the post itself, the “offset” or setback as also called, is the distance between that line and the *centre point* of the saddle rails.

So, 5 mm offset means the centre line of the rails is just behind the imaginary centre line of the post, 20mm is more.

This is important in setup to get you in the correct position relative to the bottom bracket and is influenced by the actual frame geometry.

“Most” road bikes are designed assuming a seatpost with about 20-25mm offset, but not all frames are that way.

This link shows both types on the image: right one is zero offset, left one is 32mm offset.
http://www.seatposts.co.uk/fsa-k-force-light-carbon-setback-seatpost/