One of the more frustrating things that can go wrong with a mountain bike is a seatpost that has seized to the inside of a frame. The bond can be mechanical (the result of a forced-in seatpost) or chemical (caused by corrosion). Chemical bonds typically occur between aluminum posts and steel frames, and are the result of an exchange of ions between the two materials.
Read on to find out how to prevent a seized seatpost, and tips on breaking the bond should yours become stuck.
Preparation is Paramount
One of the best ways to prevent a bond from forming is to make sure your seatpost or seat tube is well greased. Applying a generous amount of grease on the post where it enters the frame can go a long way in thwarting a permanent union. According to Park Tool, the world's largest bicycle tool manufacturer, anti-seize materials also work well in this application and may even be less affected by water and more resistant to corrosion.
To prevent a bond from occurring between an aluminum post and carbon frame (or carbon post and a steel and/or aluminum frame), once again, make sure the post is lubricated with grease or another anti-seize material. Every now and again, take out the post from your bike frame, clean it and reapply the lubrication.
Rust is typically the culprit when a steel seatpost is seized inside a steel frame. Real penetrating oil (which is made for this purpose) or light lubricating oil if penetrating oil is unavailable should do the trick.
Twist and Pull
If your seatpost appears to be seized, take the following steps:
- Take the seatpost bolt off the frame completely, don't just loosen it.
- Make a mark on the post so you’re able to tell if you’re making any progress.
- Grab a hold of the saddle and twist back and forth while pulling up. (Using the saddle works much better than using a wrench or pliers.)
- If there is no progress made, apply some acidic liquid to the mix. (i.e., lemon juice, soda, even lubricant or penetrating oil)
- Wait a bit for the acid to penetrate, and try the twist-and-pull method again!
Get More Leverage
If you cannot get the post to twist or pull up after following the method described above, you might need more leverage. In that case, Park Tool recommends removing the saddle and wheels from the bike and mounting the bike upside-down with the post clamped in a vise. This way, the frame can be used as a lever. Note that this method will only work on seatposts with a one-piece saddle clamp. Take special precaution not to pull on the rear dropout.
In some cases, however, a seatpost can be permanently bonded to the frame, and will not budge, no matter how hard you struggle. In this scenario, it's best to take your bike to a bike shop where they will likely take a hacksaw to the seatpost.