carbon seat post to carbon seat tube - necessary to loosen periodically to prevent seizing in place?

Question

I recently (about 4 months ago) purchased a bike with a carbon frame (i.e. carbon seat tube) and a carbon seat post. I've read some nightmare stories about having to replace an entire carbon frame in some cases when the seat post gets severely stuck to the seat tube.

When I first received my current bike (to reiterate, carbon seat post and seat tube) after I positioned the seat I used carbon assembly paste between the seat post and tube so as to prevent any temptation to overly tighten the seat post clamp bolt. From what I've read, carbon assembly paste is generally recommended for carbon on carbon seat posts and also stems to carbon handlebars.

The carbon assembly paste seems to hold the seat post in place great, I don't have to overtighten the seat post clamp bolt at all and the seat has never slipped.

My concern now is, how do I know the seat post and seat tube won't freeze together over time?

I use my bike for communing daily and keep it in my apartment at night, but it does have to stay outside on a bike rack (through all seasons in Michigan) during the day.

Is it recommended every so often (ex. once every month, or some other time frame?) to loosen and move the seat post to prevent freezing? Or is there some other recommended measure I can take to prevent freezing? I would prefer to continue using the carbon paste unless this is likely to cause a freezing problem.

Answer 1

A carbon seatpost will not freeze in a carbon tube much unlike metal to metal contact. So there is no need for the procedure you envisioned.

Using the carbon paste is highly recommended in your situation and also with metal/carbon contact. However you should never ever use any kind of grease or fat which might damage carbon components.

Consider investing in a torque wrench because it is near impossible to 'measure' the correct value with the wrist-o-meter. The recommended applicable torque is often printed on the clamp, like 3-5Nm. You should apply the lowest value first and increase the torque only of the post slips.

Answer 2

Sorry, but a carbon seat-post can freeze in a carbon frame if enough grease, grime and grit manage to work their way down.

This happened to me, I, like the person above thought that it couldn't seize but much to my horror it did.

Try the following,

1. Remove/ loosen clamp Try riding the bike on bumps and getting your body weight on it.

2. Hit the saddle horizontally and vertically with the heel of you hand, if you get to move just a wee bit it may then wiggle free.

3. Try heating and cooling the frame and post using hot water... This definitely works for metal due to differences in conduction of heat in different alloys, some armchair experts reckon it cannot work with carbon on carbon, this is contrary to the basic laws of chemistry. But despite the debate their will be no harm in trying.

4. Try using a lube like WD or GT in the steps above- again some folk reckon this dissolves the carbon matrix.... perennial myth from the first carbon matrixes that were produced.. modern composites should not be affected so worth a try as not likely to harm the bike.

5. Remove the saddle and hit the post into the frame with a mallet... if it moves- stick the saddle back on and wiggle it out.... I got this far, it moved in a little bit but I still couldn't remove mine.

6. Drill through the seat post closed to the frame and stick in something metal, to act as a spindle to provide more torque than the saddle did, use this to twist it out. I used a metal rod- about 2ft long I think it was 8mm diameter. This worked for me.

After doing all this I found this post... http://sheldonbrown.com/stuck-seatposts.html#carbon the theory is sound- not sure how practical it would be

A final destructive step, admittedly I didn't get this far so cannot vouch for it and I reckon you would only really get one shot at it.... compress the post at the drilled holes until it breaks- and voila you should be able to pull the pieces out, sounds too easy and I would be reluctant to try this but worth considering if all above has failed.

When you put your new seatpost in... degrease the post and inside of the frame, buff it dry with a microfiber cloth and apply carbon paste, tighten the clamp to the recommended torque and, for the love of the wee man, remove the post and clean and reapply carbon paste at least yearly!