Scrod,

I have a 2008 Schwinn Madison and need a new seat post. If I remember correctly (can't find the thread right now), the correct seat post size is 27.0 mm. The previous owner installed a 27.2 mm post. It's a tight fit and the post is pretty scratched up. Can/should I go back to a 27.0 post? Seems like there should be enough flex in a steel frame/clamp for it to work.

Also, is there a thumb rule (like X times seatpost diameter) to follow for minimum insertion depth if it isn't marked?