Technical Q&A with Lennard Zinn – Permanent seatposts and what to do about them
Stuck on you
I currently have two carbon seatposts that are stuck. Both are CampyRecord carbon and one is stuck in a Ti Litespeed Ghisallo and the otheris stuck in an aluminum Colnago. My question is how the heck do you getthem out without destroying the frame? I understand the post may be ruinedbut the frames are very expensive.
I have an aluminum Bianchi FC frame with a carbon Campy seatpost. Thething is completely seized, will not budge at all. We’ve tried heat, tappingit, taking the saddle off and putting a wrench it to torque it, etc butnothing will make it budge. I have used the same seatpost on 2 previousaluminum Bianchi frames and never had a problem. I clean regularly, especiallyafter any rain. However I do not regularly take the post out.
I have a Look 281 frame and a Look ergopost 2; the post is completelystuck in the frame. The frame has aluminum lugs and carbon tubesand the post is carbon; I suspect that corrosion of the aluminum has
caused this. The only thing that I have read as advice for breakingdown corrosion of aluminum is to apply acetone. Is this reasonable?
Is there anything else that could work better?
I have a big problem – my expensive Easton carbon seat post is utterlystuck in my even more expensive 3D Rover Scandium seat tube. Whatcan I do?
ScottDear Rudy, Matthew, John, and Scott,
With the exception of Rudy’s Ghisallo, all of these carbon seatpostsare seized into aluminum. It is possible that the Ghisallo also has analuminum sleeve in the seat tube; I can’t remember how that frame is done.Galvanic corrosion between carbon and aluminum is an issue we have discussedhere before, and to combat it, you either need to wrap the seatpost witha layer to shield it somehow from the aluminum (there are some lettersbelow with suggestions about that), or you need to pull it out frequently(certainly after any ride in the rain), clean it, and re-grease it (or,as we have discussed here as well, to prevent seatpost slippage, re-coatit with carbon assembly paste, available from Tacx, Ritchey or FSA). Corrosion-dissolvingagents are mentioned below. And, once again in answer to a constant questionI receive, grease and solvents other than paint remover (the stuff thatactually dissolves the paint off of a bike) will not damage a carbon seatpost.As for removing the post, here is a section from “Zinn and the Art ofTriathlon Bikes,” a book I just finished last Tuesday. It should be outin May or June.
|REMOVING A STUCK SEATPOST
This is a serious job; if you make a mistake, you run the risk of destroyingthe frame. If you’re not 100 percent confident in your abilities, go tosomeone who is—or at least to someone who will take responsibility if theyscrew it up.
If you still insist on getting it out yourself, you need to sit downand think about it for a while. Will the guy at the machine shop reallycharge you so much money that it is worth the risk of completely destroyingyour frame?Do you still insist on doing this yourself? Okay, but don’t say I didn’twarn you.With a hacksaw, cut off the post a little more than an inch above theframe. Remove the blade from the saw and wrap a piece of tape around oneend. Hold the taped end and insert the other end into the center of thepost. 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 stuckin your frame. Be careful; this is where many people cut too far and goright 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 screwdriveror a pair of pliers. Be careful here too. Many home mechanics have damagedtheir frames by prying too hard.
Once the wedge is out, work the remaining piece out by curling in theedges 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) forreconditioning brake cylinders, is an excellent tool for the purpose. Turnthe frame upside down, put the hone in an electric drill, and be sure touse plenty of honing fluid or cutting oil as you work. If you do not knowhow to use a hone, it may be best to take the frame to a bike shop to havethe job done or try sandpaper wrapped around your fingers.Inasmuch as removing a stuck post is so miserable that no one wantsto do it twice, I do not need to remind you to grease the new post thoroughlybefore inserting it in the frame; then check it regularly as I’ve suggestedabove.
LennardTacx for Ti?
I have a slipping carbon seatpost problem. My old Dura Ace aluminumpost was rock solid, but when I replaced it with a Controltech carbon seatpost I’ve had slippage problems. I have the Campagnolo seat clamp on myMerckx Millennium Cubed titanium frame, and I have degreased and cleanedthe seat tube out thoroughly before I installed the carbon post.My local bike shop suggested Tacx carbon build paste as a potentialsolution, but I’m nervous. The Tacx bottle mentions that it is suitablefor: steel, aluminum and carbon, but not titanium. Will I freeze my postin the frame with the build paste?
No, it will work fine in titanium as well.
LennardIs the aluminum in there?
Is there a problem with carbon seatposts and titanium seat tubes?I’ve got a Merlin and want to try using a carbon seatpost. Also, I knowthat aluminum and carbon don’t mix, but if one wanted to use a carbon seatpost in an aluminum bike, is there anything that can beused or done to mitigate the problem?
Rudy’s problem to the contrary, titanium should not be a problem, asit does not corrode, but if there is an aluminum sleeve in the seat tube,it can be. Besides the things mentioned above to mitigate it, here aresome other possible solutions from readers.
The carbon fiber seatpost problem is twofold:
1. Galvanic corrosion between dissimilar materials.
2. Clear coat reaction to solvents and grease.
To eliminate the affects of galvanic corrosion, a barrier of non-conductivematerial needs to be placed between the carbon fiber and metallic material.It is common practice in the composite industry to use as little as a .005″thick layer of fiberglass to eliminate galvanic corrosion.Clear coat is only used in the consumer market to enhance the look ofcarbon fiber, decals, paint, etc. We never use clear coat on the commercialor military composite components we build as it adds unnecessary weightand cost to the product.As for the use of solvents to clean carbon fiber, how do you think weclean our parts and molds? Chemical paint removers (strippers) containsolvents that are damaging to the resins in composites, but common degreaserslike MEK and acetone are as harmless as alcohol or vinegar when appliedwith a rag and not left to soak for days on end.Solutions:
1. Bike and component manufacturers need to addressthe problem of galvanic corrosion by adding fiberglass to any area thatmay ever come in contact with metallic components, just like Craig Calfeedoes.
2. Eliminate the clear coat. A nice shine is neat, but that’sall it does. If you are worried about a few grams on your wheel set, thenwhy aren’t you worried about 200 grams of clear coat on your bike frame?At the very least, eliminate it on surfaces like the seatpost where gallingmay occur.
Contour CompositesThe spirit of slippage
I’ve found that by wiping my carbon handlebars (on a XC rig) with methylatedspirits and then wrapping with one layer of writing paper, before clampingwith the stem (Aluminum, not carbon), has worked. No slippage atall. Grease, even natural hand oil, seems to be the slippage culprit.
KarlDon’t crush that post, hand me the pliers
From my experience working with a carbon fiber seatpost company, thereason they say not too grease a CF post has nothing to do with a reactionwith the carbon. It’s more to do with the tendency for people, whensomething slips, to over-tighten things. By not greasing the post,it decreases the chance that it will slip in the frame and, in turn, decreasesthe chance that people will over-tighten and crush a carbon tube.
Technical writer Lennard Zinn is a frame builder (www.zinncycles.com),a former U.S. national team rider and author of several best-selling bookson bikes and bike maintenance including Zinn& the Art of Mountain Bike Maintenance, which is now availableas a 4-hour instructional DVDZinn& the Art of Road Bike Maintenance, and Zinn’s Cycling Primer:Maintenance Tips and Skill Building for Cyclists. Zinn’s regular columnis devoted to addressing readers’ technical questions about bikes, theircare and feeding and how we as riders can use them as comfortably and efficientlyas possible. Readers can send brief technical questions directlyto Zinn. Zinn’s column appears here each Tuesday.