Generally, the size will be stamped at the bottom of your current seat post. Most seat posts have the size stamped into them. If you remove the post from the bike, it should be stamped near the maximum height line. How do I install my new seat post and set it to the appropriate height?
Alloy seatposts should be greased before installation. Carbon seatposts should NOT be greased, as the grease makes the carbon expand. Solid beeswax is a much better alternative. The basic formula for finding the right seat height is this: When you are sitting comfortably on the saddle with the balls of your feet on the pedals, your knees should have a very slight bend in them (they should not be locked). Ifyou then put your heels on the pedals, your legs should be straight, almost to the point where your knees lock, but not quite.
