Saturday, February 7, 2015

The Straight Goods on Removing a Stuck Seatpost

I know this is a running blog, but I have a non-running confession to make: I have a bike problem.  I really like all kinds of bicycles, but there are a few that stick in my head.  I also like building bikes, perhaps even more than riding them - and I really like riding them.  I know that I already have too many for one person to ride, but I am a sucker for a good deal, especially when one of the models that have been sticking in my head shows up on Kijiji or Craigslist or on the curb on garbage day.  In the summer of 2013, I found a 1995 17" Kona Lava Dome - one of "those" frames.  I really like steel and have always admired the Lava Dome's geometry and skinny little tubes.  Because I already have too many bikes in various states of (dis)assembly, it was a complete impulse buy, but for $20 I felt I couldn't go wrong.  That is, until I went to pick it up...

I had already committed to the fellow that I was going to buy it, and he was a nice guy who was running a neighbourhood bike repair shop out of his garage.  It had been well used and the paint and decals have had it, but the steel is in good shape.  It's nothing that some paint stripper and a wire brush can't clean up.  When I looked the frame over, however, he told me that a previous owner had inserted a "shim" in the seat tube and that I would need to get a really skinny seatpost to fit.  I immediately identified the "shim" as an old seatpost.  The nasty thing is that the seatpost was inserted deep into the seat tube and the previous owner had cut off the seatpost flush with the top of the tube.

 Upon further inspection (and repeated measurements), I discovered that there wasn't just a small portion of seatpost in there.  The section of seatpost in the frame was 28cm (approximately 11.5"), and there was nothing protruding from the tube to grab onto.  Furthermore, it became clear very quickly that the seatpost was heavily oxidized and fused to the inside of the seat tube.

I checked with Mr. Google (OK, I researched this to death) and found many different methods that many different folks have tried with varying degrees of success.  Many of these methods depended on a portion of seatpost extending beyond the frame to give the extractor something to grab or clamp with a pipe wrench or clamp in a vice, which for me was a non-starter.  Being in Canada, I made the best use of Winter to try to leverage thermal coefficients by putting the frame outside when it was -30C and then bringing it inside where I went at it with a heat gun.  Perhaps I could never get the timing right or I could not focus the heat well enough.  Research informed me that aluminum expands and contracts 2.5 times faster than chro-moly steel. So that didn't work either.

My longest experiment was with chemicals.   I looked into using chemicals to dissolve the aluminum, such as sodium hydroxide (commonly used in drain clog removers).  I saw folks who had great success with caustic soda/lye: here and here.  I read that others had success with pure ammonia, but that was hit and miss.  When I tried drain cleaner, I had trouble sealing the seat tube well enough to contain it, and when I managed to keep it in, it did nothing.  Be warned if you go this route: if it leaks on to anything metal, it will cause rust to form instantly.  I lost a really good pair of cable cutters in the process.

Sheldon Brown has a great article on removing a stuck seatpost.  (Surprise, surprise.  He has great articles on all things two-wheeled.)  The more research I did and the more things I tried, the more options I eliminated for my situation and the more I resigned myself to the fact that I was going to have to pursue the route of #12 in Mr. Brown's article: hacksawing the post out.  My problem is that there isn't just a couple of inches of seatpost in the tube, which means that I just can't use a portion of a 10" (standard ) or 12" hacksaw blade, like his article suggests.  I need something that will make these cuts down the entire length of the frozen seatpost.

The saw I needed was not available in stores.  I didn't even bother to check; I just knew.  To make my own, I started by cutting a wooden dowel (two, actually, but I will get into that later) lengthwise and epoxied a hacksaw blade in the kerf, ensuring that an even amount of blade was exposed from end to end and that enough blade protruded from the dowel to cut all the way through the thickness of the wall of the seatpost.  I also had to shave down the dowel to fit inside the seatpost.  I did this with a spokeshave plane, rasps and finally sandpaper.  If you look at the photo below, you will see a blue mark I made with a Sharpie on the handle of the saw (Mk II) just above the end of the blade.  This was a depth gauge to let me know that I was sawing deep enough into the seat tube.

Blade direction is important.  I built my first saw (Mk I) with the teeth pointing toward the handle.  In order to start the cuts in such a confined space, I wanted to be able to jam the saw into the seatpost and then cut on the pull stroke.  After the cuts were started and there was a noticeable groove in the inside of the seatpost, I used my other saw (Mk II) with the teeth pointing away from the handle, like any other conventional saw.  Cutting on the down (or push) stroke removes much more material that cutting on the pull stroke.  After many hours, here is the outcome...

Please learn from a mistake I made.  I tried to cut the seatpost into four pieces, making cuts at 12, 3, 6 and 9 o'clock.  The photo above does not show it well, but the big piece on the left is almost completely cut in half.  In retrospect, I should have made three cuts at 2, 6 and 10 o'clock.  I would have accomplished the same thing, but with a lot less effort. You may think that this is not a big deal. Read on. I am not exaggerating when I say that cutting is a long process.  It took me probably two to three hours per cut, maybe more.  The hacksaw blades were new and, therefore, sharp.  The problem is applying enough downward pressure at the very end of the saw to cut the metal.  I pulled out the frame and the saw (with newsprint on the floor to catch the shavings) whenever I watched something on television. Here is the same photo showing the outside of the seatpost.

With the seatpost finally out, you can see how much oxidization there was.  I don't think I would have ever been able to get anything to penetrate the "space" between the inside of the seat tube and the outside of the seatpost.  I also discovered that the previous owner who installed the seatpost (not the guy from whom I bought the frame) had installed a standard (or at least a prevailing standard) 27.2mm diameter seatpost.  I'm sure he had a difficult time and I don't know to what he resorted to insert it.  A very quick bit of research on the frame turned up the fact that the 1995 Kona Lava Dome takes a 27.0mm seatpost.  It is not exactly a square peg in a round hole, but 0.2mm turned out to be a big difference in this project.  Removing the seatpost took much longer than it should have.  I hope that it goes more quickly for you.

So, you ask, where am I going from here?  I have been amassing parts for the build over the past 18 months.  I'm not the kind of guy who builds a bike and hangs it on the wall to admire as art.  I build bikes to ride them.  With all of the trails around our place, I decided a build up the Lave Dome into gravel grinder.  I already have a set of Gary Fisher forks, a headset, Masi stem and drop handlebars, Shimano STX LE crankset, and 26"wheelset.  My next task is to strip the frame and have a cable stop brazed on so that I can use v-brakes on the rear wheel.  If you have any questions or comments or even a similar experience, I would love to hear them in the comments section below.  I hope that this helps someone.