Stuck seat post in a Bianchi

[messenger390]

Hello, I was not sure which forum to write this in so forgive me if it is the wrong one. I just picked up a Bianchi Volpe ,which I believe is a 2008. The seat post is stuck in the frame. I have been soaking it for days with PB blaster with no success. The problem has compounded now, as I was trying to twist the top aluminum bracket that is pressed in the post, and it is now moving without the post. I am afraid the bracket will completely separate from the post, leaving me with about 1/8" of the actual post to work with. Any thoughts or suggestions are appreciated. Thank you

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Yeah that's a pickle alright. I've worked as a mechanic in bike shops for many years and this problem seems to come up too often. It's called a slip fit joint and the OD of the post and the ID of the seat tube are supposed to be within .1mm of each other. A pretty tight spot, kinda like extending legs on a camera tripod.

The aluminium seat post and the steel frame have likely cold welded together. Perhaps there was not enough corrosion inhibitor (grease) applied during assembly.

And then having just 1/8 to get purchase on makes this extra tricky. (why was the seat slammed down? bike too big?)

Anyway, that's all history now.

What to do in the present? I've heard of a local mechanic around here (Toronto) that uses comealongs and 10 ton chains anchored from a structural beam in combination with a set of welding torches that has never met a seat post that can't be unstuck. His work often requires a repaint of the seat tube. It works, but I thought the aluminium post would expand faster than the steel seat tube but I think it's when the post cools down that the weld breaks.

What would I do if I were you? Best idea I've seen in these comments is a sawzall with .5" x 1 foot long metal cutting blade (does anyone even make those?) and (very very very carefully) cut the seat post into two equal pieces. Then get a super long super thin chisel to break the cold weld. Then find a hone to refinish the inside of the seat tube.

I've also used the lye/baking soda chemical removal once and it turned the post into putty and I had to remove it with a tiny spoon. Careful that stuff is caustic and it burns! Don't think I'll do that again.

I would not recommend putting a new tiny seatpost in the old one, because I don't think you will find one that fits perfectly. I think you might find one pretty close, but would not be surprised if the seat slowly went lower and lower further and further into the ride.

There's probably more ideas I can't think of, but hey it's not rocket surgery, right?

edit: found this link : https://www.sheldonbrown.com/stuck-seatposts.html

also a case study : http://teammaxbo.blogspot.com/2010/12/caustic-bike.html


another edit : found this link :

If that doesn't work find a nice Surly Cross Check frame in the right size and move the parts over to that. It might be easier.

Hope this helps.

 

[Bendix]

There are always tons of bizarre, apocryphal 'solutions' to this problem...

IMHO If you'd just started with the bare hacksaw blade, cutting until you have 3 pieces of seatpost and then knocking them loose with a hammer and small chisel, you'd have had that post out 3 pages ago.

Unless some doofus buried a 400mm MTB post in that frame...

 

[bleedingfingers]

I read somewhere that ammonia is what free's up the chemical reaction between the two metals .
Turn it upside down .
Dump a load in anyway you can and seal it up and let it soak .
I have done this a couple of times takes patience but it worked for me .
They didn't just pop out either still going to take some muscle to bust it loose

 

[Kickstand3]

After a good lube penetration ... lol . Put the seat end in a vise tighten and turn the whole bike frame.

 

[petritl]

I’ve been through this once. The penetrating oil and ammonia soaks were ineffective for me.

The seat post was mounted in a vise and attempted to use the frame as a lever to twist the post loose; didn’t work.(broke the end off the seat post)

I ended up cutting the seat post nearly flush with the frame and drilling the inside of the stuck seat post to a larger size to reduce its wall thickness and then used a hacksaw blade (sawzall blade wasn’t long enough) to cut two slots in the post.

The post was still stuck to the seat tube but was able to be knocked loose with a small punch.

 

[Superman1984]

I have yet to run into a seat post that kicked my butt. Damn seized or welded pedals; I won't lie since they were cheap nothing special of value bikes & cranks ....jus' cut'em off. Maybe this Bianchi isn't for the OP if the seat post whoops them

 

[coasterbrakejunkie1969]

I'm on the sawzall cut inside the tube. Would it be a possibility to gat a machine shop to bore out the old post with properdrill bit and press? Just a suggestion I mean were sending vehicles to mars, so this does not seem so outrageous.

 

[coasterbrakejunkie1969]

I would be willing to try it with a hand drill and the frame on a vice. Even if the bit is smaller it would reduce the thickness of the seat post and give more of a chance to cut and roll it inwards and perhaps remove it.

 

[SirMike1983]

I get the Sawz-All idea, but I'd never have that much control. Maybe I don't use a Sawz-All enough, but I'd opt for the hacksaw blade instead of the Sawz-All. I'd use the hacksaw blade in a manner similar to a keyhole saw, which is basically a sharp saw blade with a handle at the end.

I would avoid jimmying a smaller seat tube into the sleeve.

 

[HerrOtto]

I tried the old stem trick and it did not work. I actually think the tighter I would make the stem bolt, It forces the wedge tighter in the post, but also pushes the post out into the tube.