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Technical FAQ: Stuck seatpost remedies

  • By Lennard Zinn
  • Published Oct. 27, 2009
  • Updated Nov. 5, 2013 at 5:33 PM EST

Catharine Pendrel's seatpost - not likely to be stuck.

Question: I recently tried to adjust my saddle height on my Trek Fuel 98 and unfortunately found that it is no longer adjustable. I have an aluminum seatpost and the frame is carbon. I don’t think I put any grease on it as I was told not to grease a seatpost that goes into a carbon frame (grease degrades carbon?). I don’t think I’ve moved it for about a year and a half.

In retrospect, I should have taken it out and cleaned it once a month or so and reinserted it so I would not have this problem. Do you have any suggestions for how I can remove it and how I can prevent this from happening again besides constantly cleaning it? I tried twisting, heating up the area with a blow drier, cooling it down with ice, dripping chain lube around where the seatpost enters the frame, but nothing has worked thus far.

-Ryan

Ryan,
Grease does not harm carbon. Use it in the future. And if it slips down, use carbon assembly paste (Ritchey, FSA, Effetto Mariposa).

You are having this difficulty because you did not periodically remove the seatpost, invert the bike to drain water out of the seat tube, and let it dry out. I do this with my bikes after any ride in the wet or after washing them. The frequency depends on the conditions you are riding in. With a steel, aluminum, or magnesium frame, spray oil (or better yet, “Frame Saver”) into the seat tube to arrest the corrosion process. Re-grease the post and the inside of the seat tube, and then reinstall it (use carbon assembly spray or paste if it’s a carbon post).

As you said you want to adjust your seatpost, I’ll answer fully. But another option is to accept that you have a stuck seatpost and leave it permanently in place.

Removing a securely stuck post is a challenging job because of the risk involved. It may be best to entrust this job to a shop, because if you make a mistake, you run the risk of destroying your frame. If you’re not 100 percent confident in your abilities, go to someone who is — or at least to someone who will be responsible if they screw it up.

You’ve done the first three steps I’m sure and sort of done the fourth step (although CO2 is more effective for cooling it than ice).

  1. Remove the seat-lug binder bolt.
  2. Squirt penetrating oil around the seatpost, and let it sit overnight. To get the most penetration, remove the bottom bracket, turn the bike upside down, squirt the penetrating oil in from the bottom of the seat tube, and let it sit overnight.
  3. The next day, stand over the bike and twist the saddle.
  4. If that doesn’t work, go through the same procedure using ammonia or Coca-Cola instead of penetrating oil. Both of these are good at dissolving corrosion.
  5. If step 3 does not free the seatpost, warm up the seat-lug area with a hair dryer to expand it. If there is a big enough hole from the bottom bracket into the seat tube, pour dry ice in, and let the post get really cold. If not, discharge the entire cartridge of a CO2 inflator at the joint of the seatpost and the seat collar to freeze it and shrink it. (A poor alternative still worth trying is to ice the exposed seatpost with a plastic bag filled with crushed ice.) Now try twisting as in step 3.
  6. If step 5 does not free the seatpost, you will need to move into the difficult and risky part of this procedure:
    (a) You will now sacrifice the seatpost. Remove the saddle and all of the clamps from the top of the seatpost. With the bike upside down, clamp the top of the seatpost into a large bench vise that is bolted to a very secure workbench.
    (b) Congratulations, you have just ruined your seatpost. Don’t ever ride it again.
    (c) Perform the heat/ice or CO2 trick from step 5. Grab the frame at both ends, and begin to carefully apply a twisting pressure. Be aware that you can easily apply enough force to bend or crack the frame, so be careful. If the seatpost finally releases, it often makes such a large “pop” that you will think that you have broken many things!
  7. If that did not work, cut off the seatpost a few inches above the seat lug and clamp the top of it in a vise. Warm up the seat-lug area with a hair dryer to expand it. Discharge the entire cartridge of a CO2 inflator down inside the seatpost to freeze it and shrink it. Now try twisting as in step 4.
  8. If step 6 or 7 does not work, you need to go to a machine shop and get the post reamed out of the seat tube.

Do you still insist on doing this yourself? Okay, but don’t say I didn’t warn you.

Take a hacksaw and cut off the post a little more than an inch above the frame. Remove the blade from the saw and wrap a piece of tape around one end. Hold on to the taped end and slip the other end into the center of the post. Carefully — very carefully — make two outward cuts about 60 degrees apart. Your goal is to remove a pie-shaped wedge from the hunk of seatpost stuck in your frame. Be careful; this is where many people cut too far and go right through the seatpost into the frame. Of course, you wouldn’t do that, would you?

Once you’ve made the cut, pry or pull this piece out with a large screwdriver or a pair of pliers. Be careful here, too. A lot of overenthusiastic home mechanics have damaged their frames by prying too hard.

Once the wedge is out, work the remaining section of the post out by curling in the edges with the pliers to free more and more of it from the seatpost walls. It should eventually work its way out.

With the post out of the frame, clean the inside of the seat tube thoroughly.

A flex hone, sold in auto parts stores (or rented at rental stores) for reconditioning brake cylinders, is an excellent tool for the purpose. Turn the frame upside down, put the hone in your electric drill, and be sure to use plenty of honing fluid or cutting oil as you work. If you do not know how to use a hone, it may be best to take the frame to a bike shop to have the job done or try sandpaper wrapped around your fingers.

Inasmuch as removing a stuck post is so miserable that no one wants to do it twice, I’m certain that I do not need to remind you to grease any metal seatpost thoroughly before inserting it in the frame, and check it regularly thereafter as previously outlined. Carbon seatposts have a soft, clear-coated exterior and can mechanically lock into the frame or be held in by corrosion of the seat tube or seat tube sleeve, so I recommend carbon assembly spray or paste to reduce these dangers.
-Lennard

Question: My wife has an original Bontrager Race Lite frame with an original Bontrager/Titec Race Lite carbon fiber seatpost. Now the head is loose on the seatpost, and the seatpost is stuck in the frame. I would like to remove the seatpost without destroying it, but have not been able to after soaking it for weeks with penetrating oil. I contacted “Bontreker,” but their only suggestion was try loosening it with 3-i-n1 oil. I have been looking and can’t find any suggestions for loosening carbon fiber stuck in steel.

Any suggestions?

-Paul

Paul,
It sounds like the seatpost is already ruined, if the head is loose. Get it out as above or use the below cool suggestion from my friend Don Palermini, senior brand manager of Bell Sports specialty division.
-Lennard

Another suggestion: Regarding the removal of a seized carbon post from an aluminum frame … I’ve successfully removed two seized carbon posts by, 1) squirting penetrating oil around the post at the seat collar junction, 2) cutting the top of the post off with a hacksaw, 3) taking the quill stem and handlebars off my Electra cruiser and ‘installing’ them into the seized post (the quill needs to be down below the seat collar), then 4) used the wide handlebars for leverage, worked the post back and forth until the post breaks free.

While it certainly dooms the post, done carefully, it should not do any damage to the frame. I’m sure any old quill stem/handlebar combo would work … the cruiser bars just give you enormous leverage.

-Don

Another response: Don’t crush that post, hand me the pliers.

From my experience working with a carbon fiber seatpost company, the reason they say not to grease a CF post has nothing to do with a reaction with the carbon. It’s more to do with the tendency for people, when something slips, to over-tighten things. By not greasing the post, it decreases the chance that it will slip in the frame and, in turn, decreases the chance that people will over-tighten and crush a carbon tube.

-Andy

Another solution: I have a simple solution to removing a seatpost that is stuck to the frame. It took me about an hour of sweat and upper body strength, but it was worth it. I sacrificed my Columbus carbon seatpost and not my Moser Limited edition Columbus Starship aluminum frame.

Clamp your bike to a rear wheel trainer.
A. Remove the saddle from the seatpost and clamp on (2) large flat head screwdrivers.
B. Remove the collar ring and pour some olive oil around the seatpost.
C. Sit on the top tube and twist the screwdrivers left and right a couple of times with an upward force. Do this as many times until you see the frame move in increments.
D. Hammer the screwdrivers with an upward motion a couple of times.
Catch your breath and have a drink of water.
Repeat step C and D as often until you see the post rise from the top tube.
Once you see the post rise about an 1 to 2 inches, twist the post 360 degrees left and right with an upward motion.
Waa laa, your post is removed, and bike frame saved.

Don’t follow manufacturer’s recommendation, lube your post with Shimano grease.
This was my second carbon post stuck in an aluminum frame.

-John

Another solution: I recently purchased a bicycle with an aluminum frame and a carbon fiber seat post so the recent accounts of stuck seat posts have both frightened and puzzled me.

The reason for fear is clear but I am puzzled that galvanic corrosion is cited as the reason that carbon fiber seat posts are seizing in aluminum frames.

Galvanic corrosion requires that two electrically conducting materials be in contact in the presence of an electrolyte. Obviously, the aluminum seat tube is conductive and the electrolyte is moisture that gets trapped between seat post and tube.

But, although carbon fiber is electrically conductive, the resin it is embedded in and covered with is not, so it seems to me that the carbon fiber composite is not electrically conductive so galvanic corrosion cannot occur.

A quick check of my composite seat post with an ohmmeter confirmed that it is not electrically conductive, or at least has a very high resistance at the test voltage of the meter. What I believe is happening is simply that the aluminum seat tube is oxidizing and the oxide deposits build up between the seat post and tube eventually seizing the post. The clearance is generally small and it might not take too much oxide build-up to stick the post.

A simple way to prevent stuck seat posts is to remove the seat post and clean out the tube regularly, especially if the bicycle is ridden often in wet conditions. A little Scotch Brite pad on a stick should do the job very well. That is going to become a regular part of my bicycle maintenance.

-Bob

Follow Lennard on Twitter at www.twitter.com/lennardzinn


Technical writer Lennard Zinn is a frame builder (www.zinncycles.com), a former U.S. national team rider and author of numerous books on bikes and bike maintenance including the pair of successful maintenance guides “Zinn and the Art of Mountain Bike Maintenance” – now available also on DVD, and “Zinn and the Art of Road Bike Maintenance,” as well as “Zinn and the Art of Triathlon Bikes” and “Zinn’s Cycling Primer: Maintenance Tips and Skill Building for Cyclists.”

Zinn’s regular column is devoted to addressing readers’ technical questions about bikes, their care and feeding and how we as riders can use them as comfortably and efficiently as possible. Readers can send brief technical questions directly to Zinn. Zinn’s column appears here each Tuesday.

FILED UNDER: Bikes and Tech / Mountain / MTB / Road / Technical FAQ TAGS: / / / /

Lennard Zinn

Lennard Zinn

Our longtime technical writer joined VeloNews in 1987. He is also a framebuilder, a former U.S. National Team rider, and author of many bicycle books, including Zinn and the Art of Mountain Bike Maintenance and Zinn and the Art of Road Bike Maintenance, as well as Zinn and the Art of Triathlon Bikes and Zinn's Cycling Primer: Maintenance Tips and Skill Building for Cyclists. He holds a Bachelor’s degree in physics from Colorado College. Readers can send brief technical questions to Ask LZ.

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