Seized carbon seat post on carbon frame - HELP!

[SCD]

If all lubing tricks fail make thermal expansion work for you. With regards to the earlier report: I doubt that this can crack your frame. It is expanding the frame, against restraint, so no stresses should be created.

Make an ice bucket and stick the seat post in, saddle attached. Immerse just to the clamp. Leave for 60min until it is proper cold and had time to cool down inside the frame as well. Now soak a towel in boiling water and wrap over the 100mm of frame at the clamp (Use hand protection if you don't want to lose your skin!). Let heat up for 1-2min. 

Now with the frame help by an assistant us the saddle to torque the post loose and work it out.

Good luck

[sirmoun10goat]

I've worked on a few bikes were the seat post was a rather tight fit.

In a few cases this has been due to the seat post collar being too tight and the seat post has ovalised - the resin and fibres get crushed and you end up with a ridge on the seatpost. In most cases its not serious but in a few its been a real problem to get the post to move. The ovalised post also doesn't rotate in the seat tube

If that’s the case, surely no amount of penetrating fluid will help. Oil/lubricant should help, provided it can get between the seat post and frame

[mecheng89]

It took me a week to get done but I got it out. You will have to sacrifice the seat post though .

I've got a feeling I'm heading this way. None of the replies so far have instilled me with confidence that I might not wreck something. 

[Grease_Monkey]

huh?!! How did you get the clamp over the saddle cradle?

Was just thinking the same thing

[W Smith]

Coke (the cola type) down the seat tube had had many successes too.

 

Tried this before and it made no difference at all..As mentioned , a combination of penetrating oil, subtle force and luck is the way to go.

[RobertWhitehead]

Let's put on our white lab coats quickly and chat about what really happens between two surfaces of different material types: 

 

Over time there's a reaction called - Galvanic corrosion which takes place between aluminum & carbon. Here's a short write up about this: 

 

 

Aluminum Coupled to Carbon Composite

Aluminum alloys are extremely vulnerable when they are coupled to a carbon composite. According to the anodic and cathodic polarization curves of aluminum alloys and carbon composites, it is clear that the rate of galvanic corrosion in seawater is controlled by the oxygen reduction reaction.

What this means is that any condition that leads to an increase in the rate of oxygen reduction will cause an increase in the rate of galvanic corrosion. During the galvanic corrosion, a white, jelly corrosion product will be formed on the surface of the aluminum.

There is an assertion that the galvanic corrosion rate of aluminum could be mitigated by the anodization of aluminum and the formation of a thick, protective aluminum oxide layer on the surface. However, it has to be mentioned that in the case of a breach of the oxide layer by mechanical damage, the situation becomes much worse due to a really high cathode-to-anode surface area ratio (Ac/Aa).  

 

Now, what the above means is quite simple. The white layer which forms on the seat post inside the frame is actually corrosion and this takes up the space between the frame and post allowing it to seize or get stuck. Yes, I agree, penetrating oil and or something like coke which chews away at the corrosion may work, I suppose it all depends on how long you're will to wait for it to do it's job. However, especially in my case and with my experience trying to get a liquid of any viscosity to penetrate two surfaces and then remove the corrosion which has formed over a few months and or in some cases a few years doesn't make sense.

Unless, if you're using something like an acid that really packs a punch the chances of success is based on luck and the amount of force you'll apply after the oil / coke / dry ice / acid / caustic soda has done their job (or just ran through the inside of the frame and dripped out onto the floor  )

 

I am not arguing that a penetrating oil and or any other liquid wont work - some folks (as mentioned above) have had some form of success - this is fantastic (not sarcastic, I am really glad it worked out) but the amount of time the seat post and frame had for the layer of corrosion to form is equal to the amount of effort and or oil required to get it freed. In my case the seat post was installed and rode for close to 19 000km and or over a 4 year period without using carbon paste (not my doing - this was a friends bike). 

 

So how did I get the post out? 

•   I stripped the frame down - I needed to do this in any case because I wanted some of the parts for my bike
• My first couple of days I applied various forms of oils and or coke and or other liquids to mess up the workshop floor
• Then I took matters into my own hands
• I took an angle grinder and cut the seat post off about 5cm above the frame
• I then drilled a hole through the seat post big enough for a Mnr of a screwdriver to fit through
• I then took a hand saw - similar to this one: https://www.makro.co.za/hardware-auto/hand-tools/loose-tools/saws-and-accessories/mastercraft-150-mm-mini-hacksaw-/p/000000000000202937_EA 
• I then proceeded to cut two grooves on either side of the post - using a hand saw for this allowed me to feel and see once I got close to the frame (a small flashlight works great to see better). 
• With some other tools like a long nose plier, flat screw driver and other things I could get my hands on I managed to break / lift small pieces of the seat post as I went down the frame
• After the groove on both sides were all the way down the frame I proceeded to turn the frame around on the stand, push the screwdriver through the hole and smack it out with the hammer. 

 The whole process took a week to complete but I did not make a mark on the frame, the seat post however, that was not so lucky 

Edited December 22, 2020 by RobertWhitehead

[DieselnDust]

just remember we dealing with a case of carbon in carbon. Galvanic corrosion isn't the issue here, rather its just poor tolerances in manufacturing. Basically another carbon bikes in poor tolerances shocker article

[Shebeen]

just remember we dealing with a case of carbon in carbon. Galvanic corrosion isn't the issue here, rather its just poor tolerances in manufacturing. Basically another carbon bikes in poor tolerances shocker article

[hambini]shiite engineering[\hambini]

[DieselnDust]

[hambini]shiite engineering from the uranus of humanity[\hambini]

 

 

LOL fixed it for you

[SCD]

Another interesting balls-up that could happen with cheap composites. We did windsurfing parts and repairs with prepreg carbon mats that we cured at about 80C. While rockhard when cooled down they were not really hard when still at temperature. So if you put two carbon parts together and then one is a low quality part and maybe not fully cooked, then a rest in the sun could heat it up enough to activate the remaining resin and complete the cure, and welding the seat post into the frame for good

[Mook]

This might ruin your paintwork BUT it will solve your sticky problem .............

 

DOT 4 brake fluid

 

I have seen it work in automotive applications where nuts, bolts, brackets etc. are seized together. Rust or corrosion does not stand a chance against brake fluid ..................... I guess paint neither

[Kranswurm]

Let's put on our white lab coats quickly and chat about what really happens between two surfaces of different material types: 

 

Over time there's a reaction called - Galvanic corrosion which takes place between aluminum & carbon. Here's a short write up about this: 

 

 

Aluminum Coupled to Carbon Composite

Aluminum alloys are extremely vulnerable when they are coupled to a carbon composite. According to the anodic and cathodic polarization curves of aluminum alloys and carbon composites, it is clear that the rate of galvanic corrosion in seawater is controlled by the oxygen reduction reaction.

What this means is that any condition that leads to an increase in the rate of oxygen reduction will cause an increase in the rate of galvanic corrosion. During the galvanic corrosion, a white, jelly corrosion product will be formed on the surface of the aluminum.

There is an assertion that the galvanic corrosion rate of aluminum could be mitigated by the anodization of aluminum and the formation of a thick, protective aluminum oxide layer on the surface. However, it has to be mentioned that in the case of a breach of the oxide layer by mechanical damage, the situation becomes much worse due to a really high cathode-to-anode surface area ratio (Ac/Aa).  

 

Now, what the above means is quite simple. The white layer which forms on the seat post inside the frame is actually corrosion and this takes up the space between the frame and post allowing it to seize or get stuck. Yes, I agree, penetrating oil and or something like coke which chews away at the corrosion may work, I suppose it all depends on how long you're will to wait for it to do it's job. However, especially in my case and with my experience trying to get a liquid of any viscosity to penetrate two surfaces and then remove the corrosion which has formed over a few months and or in some cases a few years doesn't make sense.

Unless, if you're using something like an acid that really packs a punch the chances of success is based on luck and the amount of force you'll apply after the oil / coke / dry ice / acid / caustic soda has done their job (or just ran through the inside of the frame and dripped out onto the floor  )

 

I am not arguing that a penetrating oil and or any other liquid wont work - some folks (as mentioned above) have had some form of success - this is fantastic (not sarcastic, I am really glad it worked out) but the amount of time the seat post and frame had for the layer of corrosion to form is equal to the amount of effort and or oil required to get it freed. In my case the seat post was installed and rode for close to 19 000km and or over a 4 year period without using carbon paste (not my doing - this was a friends bike). 

 

So how did I get the post out? 

•   I stripped the frame down - I needed to do this in any case because I wanted some of the parts for my bike
• My first couple of days I applied various forms of oils and or coke and or other liquids to mess up the workshop floor
• Then I took matters into my own hands
• I took an angle grinder and cut the seat post off about 5cm above the frame
• I then drilled a hole through the seat post big enough for a Mnr of a screwdriver to fit through
• I then took a hand saw - similar to this one: https://www.makro.co.za/hardware-auto/hand-tools/loose-tools/saws-and-accessories/mastercraft-150-mm-mini-hacksaw-/p/000000000000202937_EA 
• I then proceeded to cut two grooves on either side of the post - using a hand saw for this allowed me to feel and see once I got close to the frame (a small flashlight works great to see better). 
• With some other tools like a long nose plier, flat screw driver and other things I could get my hands on I managed to break / lift small pieces of the seat post as I went down the frame
• After the groove on both sides were all the way down the frame I proceeded to turn the frame around on the stand, push the screwdriver through the hole and smack it out with the hammer. 

 The whole process took a week to complete but I did not make a mark on the frame, the seat post however, that was not so lucky 

Eerrrrmm.....both materials are carbon

[Kranswurm]

just remember we dealing with a case of carbon in carbon. Galvanic corrosion isn't the issue here, rather its just poor tolerances in manufacturing. Basically another carbon bikes in poor tolerances shocker article

Ah..already covered

[RobertWhitehead]

Sorry, my bad I read like my @ss. But in that case none of penetrative oils / Coke / heat / dry ice or any other liquid will work. A carbon seat post will come out easier than an alu one ????.

 

 

 

just remember we dealing with a case of carbon in carbon. Galvanic corrosion isn't the issue here, rather its just poor tolerances in manufacturing. Basically another carbon bikes in poor tolerances shocker article