I am helping a friend fix his bike that he got for free. Everything went well, except that I cant raise the saddle. The seatpost is really stuck in the frame.
The clamp was easily removed. When I tried to turn the saddle only the saddle itself is turning, and the seatpost remained stuck. I tightened the saddle bracket as hard as I could, and I managed to turn the seat post a few millimeters back and forth. But somehow it is even more stuck now and I can't move it at all. I am afraid that I will bend/break the bracket in the seat if I tighten it anymore.
I tried with a pipe wrench and still couldn't twist it. Perhaps I will be able to if I have another person holding the bike so I have two hands for the wrench. I did manage to damage the surface of the seat post though.
I have a few questions:
How would a professional remove the seatpost?
Why is it even stuck? Can this happen because of rust, or is it more likely because the previous owner hammered a 30.2mm seatpost into a frame meant for 30mm? I can see at the Wikipediaartikel (link) that both 29.6, 29.8, 30.0, 30.2 and 30.4mm are common sizes. As I don't have a precise caliper I can only tell you that it is approximately 30mm.
If it is because of rust, can I polish off the rust and use the same seatpost again? If so, should I polish the post or the internal part of the frame?