Stuck/Fractured Carbon Seat Post Lessons

[denvervig]

Just curious on everyone's secret sauce for carbon seat post 'management' as we were looking to get my son into a properly sized frame and found a 2006 Cannondale System Six that had some 'history' (fix gear wheelset, dirty, etc.) but was still in really nice shape otherwise. It did not even cross my mind to check the FSA SL-K seat post and sure enough, when I started cleaning it up - doh - it would not even budge. Started frantically searching google and paceline and tried some heat along with continued grunt work until it started to budge. Anyway, we finally got it out after the usual grunting/groaning as part of the twisting process. Once out, it was clear that it was also clamped down too tight as there was small horizontal fracture which is also visible from the interior of the post. Needless to say, we're going to track down an aluminum seat post...

https://photos.app.goo.gl/4NWpgjqgrcohPxvQ8

[AngryScientist]

oof. glad you got it out OK.

the ultimate key is to not leave the post in a frame for years unattended. mark the post, so you know the seat height and pull it out a few times a year and inspect.

[ultraman6970]

+1 and add... put some carbon paste to the seatpost even if aluminum seatpost. In steel frames i put grease and maybe a dab of carbon paste just in case only.

[oldpotatoe]

Once out, it was clear that it was also clamped down too tight as there was small horizontal fracture which is also visible from the interior of the post. Needless to say, we're going to track down an aluminum seat post...

My pitch here for carbon posts and external seatpost clamps..Unless you have one that is designed to stay really round when clamping(Campag comes to mind), turn the clamp around 180 degrees with a carbon post, bolt opposite the split in the frame..it helps to keep the 'hole' rounder when you tighten, less of above to happen. Looks 'kinda' goofy but it might save that lot$ seatpost..

[denvervig]

I've got the collar reversal setup on my Strong extralite frame as a result of the prior owner who is a friend of mine.

Back to the on-going saga...

We picked up a 3T aluminum post on the weekend and have a similar issue on insertion whereby no issue initially but then massive resistance after 1-2 inches. We've peered into the seat tube and looks clean but I'm assuming that there's residue from the carbon/aluminum bonding (i.e. galvanic corrosion?) given that I have no idea how long the FSA carbon seat post was in there (the 2006/2007 Cannondale catalogs indicate that an FSA post was stock). I've searched around to find out what is best to clean/scrub the seat tube but have not found anything definitive so additional ideas/insight are welcome

[unterhausen]

carbon/aluminum does cause products of corrosion. Probably best to get a flex hone and clean it out.

[r_mutt]

I use a mix of carbon paste and Phil's grease. a shop mechanic showed me the rick and thus far it's been solid. I do however take my post out at least once a year.

[robt57]

I've got the collar reversal setup on my Strong extralite frame as a result of the prior owner who is a friend of mine.

My 2015 All road Strong has a butt 4" from the top. Don't know if yours does, but you should be aware if that is the case. A 27.2 stops in mine when it get to the butt.

My fix instead of cutting a nice carbon post is/was to install a 27.2/25.4 shim and use a nice comfy Cannondale 25.4 carbon post that goes right past the butt uncut.

[sokyroadie]

A steel rod is best, but a wooden dowel will work - 3/8 or 1/2" dia. cut a slit in the end, take some emory paper (doubled up) slide it in the slit, chuck the dowel up in your drill. Works great and cheap. You wrap the emery paper up (clockwise) to get it in the seat tube, it will become a flap disc when you pull the trigger.

[Peter P.]

Interesting story. Glad you got the post out.

I agree with sokyroadie; some sandpaper in the seat tube will do the job.

[denvervig]

Thx - my son is harassing me daily to get this sorted!

[denvervig]

3M Emery cloth did the trick! There were few a spots of black carbon deposit (presumably) a few inches below the top of the seat tube that would not come off using other means but the emery took care of them in fairly easily. Seat post slides in as normal now. Thanks for the help!