Bicycles/Maintenance and Repair/Saddles and Seatposts
You should check your saddle to ensure it's secure and properly positioned. Grasp it firmly and attempt to move it out of position while holding your bike steady. Some side-to-side movement will probably occur but if your seat post shifts up and down, or your saddle feels loose, make adjustments. Also check your seat post visually to make sure you haven't exceeded the seat post extension limit line (the furthest point that the post can be safely extended upwards) has not been exceeded. This is clearly marked on the side of your seat post. Regularly remove your seat post from your frame and coat it with a thin layer of grease before re-installing it. This grease layer will help protect the post against rust and corrosion and more important prevent the post seizing in your frame.
The section below lists a number of specific actions that may be required.
Loose or poorly adjusted saddle
Proper saddle position is often a matter of personal preference. Saddles can be adjusted for height, tilt and fore/aft position. The exact combination that works best for you will depend on your physical size and your riding style. For more information about checking saddle position and making adjustments, check elsewhere in the site. Make sure your saddle is secure before every ride. Most saddles are held in place by a few simple nuts and bolts. All of them should be tight enough to resist vigorous shaking.
An over-extended seat post
This is a serious safety hazard. In general, at least two inches of your seat post should be inserted into your frame at all times. This rule however will vary considerably if you follow the growing fashion of "showing a lot of seatpost". If you have to raise your seat post beyond its extension limit line to get comfortable on your saddle, it's probably time for a larger seat post, or a bigger bike. Once you've found the "perfect" saddle position for you, mark your seat post and your saddle rails with tape or felt tip pen (indelible) so you can readjust them easily.
Regularly remove your seat post from your frame and coat it with a thin layer of grease before re-installing it. This grease layer will help protect the post against rust and corrosion and more important, prevent the post seizing in your frame.
Saddle Cleaning Procedures
To keep your saddle in good condition, simply wipe it down from time to time and treat it with UV-protective conditioner. Most models can be cleaned with light soap and a little clean water. Others require special cleaners designed for their specific materials.
Slipping Brompton Seat Posts
Some bicycles suffer from a slipping seatpost. During the ride, the weight of the rider is too much for the installed seat post clamp. Usually, the seat post clamp can be tightened without damage, but in some bicycles, notably the Brompton folding bicycle, it is harmful to tighten the clamp to the level needed by a heavy rider. (Riders who weigh more than about 80Kg). The solution for the Brompton is to set the existing clamp as usual, but to add an additional quick release seat clamp at the point where the seat post exits the frame. Setting both clamps will overcome the slippage and will not permanently modify the bike. A Sunlite QR Seat Post Clamp, 31.8mm does the job but alas, needs some modification; the inside rim of the clamp needs to be removed by filing before it will slide onto the seatpost. The use of a bench vise is recommended.