Although a lot of racing professionals don't sit on their bike seatpost to position yourself properly while riding. The seatpost, or seatpin, extends from the bicycle frame to the bike saddle by clamping on to the saddle rails.
Sizing
* The length of seatposts range from 75mm to 430mm. Mountain bikes will have longer seatposts.
* The diameter of seatposts range from 22mm to 32mm.
* The offset of seatposts, the distance between the centerpost of the seatpost tube and the centerline of the clamp area can range from 0mm to 45mm. Depending on the seat angle of the bicycle frame, an offset may or may not be needed.
Types of Seatposts
* '''Plain '''is most common on kids' or less expensive bikes. The tube decreases in diameter at the last inch and clamps onto the saddle railing with one bolt.
* '''Micro-adjustable''' is the most common type of seatposts. It can either be adjusted freely or limited to a number of positions it can be adjusted to.
* '''Integrated '''seatposts are molded into the bicycle frame itself. They are available with high-end track and road bicycles. The advantage is that the bicycle will be lighter but the lack of adjustments can pose as a problem for some riders.
* '''Suspension '''has a telescoping mechanism that allows riders to move up and down. The seatpost has a spring inside it which is helpful for insulating the bike saddle from bumps on trails. This type is most common for mountain bikes.
* '''Pivotal '''seatposts are made for BMX bikes. The top of the seatposts have concave ridges that is supposed to attach to a pivotal seat.
Maintenance
* Seatposts can seize in the frame. Therefore they must be removed, cleaned, and greased from time to time.
* Carbon seatposts may need to be maintained differently and there are special products such as carbon paste ready for preparation.
