Here is a list of questions I am regularly asked in the course of my work. If they can be of any help to you to remove your seatpost, great!  If not I would recommend seeking professional advice and this list may then be of help in finding a suitable experienced person to entrust your bike with. 

It is very easy to underestimate the challenge faced when looking at something so simple as a stuck seatpost. 

We’ve successfully (consecutively) removed over 1200 seatposts to date so we’re happy to help you too.

My seatpost will not move. What should I do?

Make sure your seat clamp is fully slackened and if possible allow it to slide off the frame.  Look carefully at the seat tube (where the seatpost goes into the frame).  Have any extras been added, e.g clamp on lights, clamp on bottle cage or clamp on pump etc?  The pressure exerted by these clamps (even plastic) can be enough to hold the seatpost firm. I’ve had customers  where the front (clamp on) derailleur was holding the seatpost in!

Can I try to twist my seatpost out?

Yes (with caution and only if the seatpost is round, i.e. not aero).  A bicycle frame is not designed for the torsional forces that can be exerted when attempting this approach.  The most force that should be applied is moderate and by hand.  Holding the seat in two hands, front and back, and twisting to and fro.  If the seatpost moves, (even a degree or two), then patience and an upward pulling twist may well remove it.

Should I attempt to clamp the seatpost in a vice and using the frame as a lever attempt to twist it out?

No, not if you value your frame!  The incorrect forces at work here are huge.  Frames can crack or fold and even if the seatpost does finally come out, the frame could have suffered irreparable damage.  Seatposts have been known to crack and even shear off at the seat clamp area.  The same goes for any method using excessive twisting force.

I have read filling the seat tube with Coca Cola will break the bond between the seatpost and the frame?

From my experience with alloy components no.  I receive many frames where this has been attempted with no noticeable result.  Out of interest I took a heavily oxidised alloy seatpost and left it soaking for weeks in a bottle of coke. When removed, it had merely been stained brown and the oxidisation was still hard and intact on the seatpost.  However with a steel frame or seatpost the phosphoric acid and lubricating effect of the liquid may be enough to allow the seatpost to begin to twist and so come out.

Will soaking with WD40/ Plus Gas/ Diesel etc help?

Be careful again here!  Some of these products will affect paintwork.  If the frame/seatpost is carbon then it is generally not recommended to use a petroleum based product for risk of softening the carbon composite.  If no carbon is present then these types of penetrating lubricants can have a positive effect, however the internal pressure exerted on the frame by, say, a heavily oxidised alloy seatpost can easily outweigh this approach.

How about heating/cooling the frame/seatpost?

Heating/cooling is generally a great way of freeing seized parts.  I cannot recommend this approach to a bicycle frame/seatpost however.  When dealing with carbon/alloy/steel/titanium mixes it is unknown what affect this approach can have on the frame and components.

What about splitting the seatpost from top to bottom with a long hacksaw blade?

In theory not a bad idea.  In practise very, very difficult and time consuming to achieve without frame marking or damage.  I receive frames where this has been attempted and almost all have saw marks or cuts in them. Not recommended. 

Should I try caustic soda, a blow lamp or oxy/acetylene equipment?

Common sense will tell you that these approaches are drastic, risky and without good experience, simply dangerous!  Paint will be damaged and frames can/will be scrapped.

This list is not intended to be complete and I will attempt to answer any question on these methods or any others that are offered.
It probably goes without saying I do not/could not attempt any of the above on a customers valuable bike.  They are simply too unknown, time consuming and/or risky.  I adopt a solid engineering approach using sound methods.  All my tooling is bespoke and handmade and I treat every job with the utmost care, be it a winter bike or a high end TT bike.  As far as I am aware I have 100% customer satisfaction.
As always please contact me to discuss any seatpost problem you may be having.   
John, The Seatpost Man.
john lee the seatpost man