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De-rusting Bike Seat-Post



 
 
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  #11  
Old March 3rd 10, 06:43 PM posted to rec.bicycles.tech
thirty-six
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Posts: 10,049
Default De-rusting Bike Seat-Post

On 2 Mar, 19:00, * Still Just Me *
wrote:
On Tue, 2 Mar 2010 10:07:41 -0800 (PST), N8N
wrote:

What are you using as a penetrating oil? *IME lots of people recommend
WD-40 which I've found to be marginally more useful than tap water. *I
like PB Blaster, Kroil, and Wuerth Rost Off, although I'm sure there
are others that work well


Agreed. Unlike WD-40, I've seen PB Blaster actually work to loosen
some very stuck fasteners. Sometimes multiple applications over
several days helps.


Whatever release agent used, it is helpful to encourage the bond to
break using shock. This is an absolute with something which is
guenuinely stuck. Use a big hmmer.
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  #12  
Old March 3rd 10, 06:52 PM posted to rec.bicycles.tech
thirty-six
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Posts: 10,049
Default De-rusting Bike Seat-Post

On 3 Mar, 03:45, AMuzi wrote:
Rick wrote:
How much too low?
Not all seats are equal in height above the mounting rails.
Try a taller seat. *Seats with excess padding or springs (or both) are
usually taller.


I have had to saw out seat posts before. *Days & weeks of soaking with
penetrating oil don't always work.


I've never had any luck with heat.


The last one was a bugger. *I removed the bb, cut the top of the seat
post off, inserted a long threaded rod, added washers and a nut to the
bottom of the threaded rod thru the bb shell. *Pull up. *I used a
large socket (1 1/16") to allow the seat post to slide up inside and
provide a pulling point against the top of the frame, with washers and
a nut on the top. *Lots of obstacles to that process like curved in
seat tube at the bottom, water bottle mounts sticking in too far,
curved top of seat lug, etc. but It worked with lots of effort but
minimal damage to the frame.


"I've never had any luck with heat"

http://www.wolframalpha.com/input/?i...point+aluminum


The melting point of aluminium exceeds that of some spelters so re-
brazing of the seat stays may be necessary if more than minimal heat
is used.

Thinking on, the use of soaking with cola then rapidly heating the
post will make the cola boil and could be enough to split the bond
without resort to heavy hammers, melting, reaming or grinding. Seems
like the lowest risk of damage.
  #13  
Old March 3rd 10, 06:58 PM posted to rec.bicycles.tech
thirty-six
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Posts: 10,049
Default De-rusting Bike Seat-Post

On 3 Mar, 18:26, " wrote:
On Mar 2, 11:18*pm, LF wrote:



On Mar 2, 11:40*am, Veganeric wrote:


I've acquired a bike that unfortunately has a seat post that is rusted
in place.


Like I told Ray:
(I hope yours is alum post in a steel frame.)


On Mar 2, 10:30 pm, Ryan Cousineau wrote:


I have a nice frame (steel) with a fairly nice (aluminum) seatpost stuck
in it.
Before I resort to cutting it up and pulling it out, I'd like to try
saving the post. So far heat (tried by someone else) didn't work, a few
days of liquid wrench and banging on it didn't work, either.
Ray,


I've loosed several very stuck aluminum seatposts in steel frames.
Here's a few thoughts:
1. *COLD is GOOD. *The alum contracts greater than the steel when
cold. *I have waited till a cold New England winter day to free a
few. *I take them outside to cool down, then bring them in, Turn the
bike upside down and put the seat post in a bench vice. *Use the
leverage of the bike, twisting and turning the frame, to free the seat
post. It can be a two person job; take care to not over torque (I
worry about damaging the frame). *The whole thing heats up with
friction. When it gets hot, I bring it out to cool down, and then
bring it in and start again.
2. *AMONIA is GOOD. *The culprit might be aluminum oxide; amonia
disolves it. It's fast acting. So, if it is going to do any good, it's
very quick -- no need to wait for it to soak over night.
3. *It's hard to get liquid into the seat tube/ seat post area.
Remove any water bottle cage bolts, and try to pour some in there.
Removing the BB, gives other possibilities.
4. It might be just luck, but I like Krell (I hear it's alot like
transmission fluid) as a lubricant for freeing stuck seat posts.


Good luck. Keep us posted (no pun intended).
Larry


Here's a possible solution from 1995:

Tom Noll
View profile
* * * * *More options Sep 14 1995, 2:00 am
Newsgroups: rec.bicycles.tech
From: Tom Noll
Date: 1995/09/14
Subject: Stuck Seat Post
Reply to author | Forward | Print | Individual message | Show original
| Report this message | Find messages by this author
Here's how I freed my seatpost after I tried everything else.

I went to the local grocery store and purchased about $6.00 worth of
dry
ice. *I packed the dry ice around the extended seat post and let it
chill
for about 45 minutes. *When the seatpost was sufficiently cool, I
twisted
the post with a large crescent wrench, and *presto* the seat post
released. *It is important to chill the seatpost and not the seat tube
on
the frame.

Some caveats, this was on a custom mountain bike frame and there was
enough of the seatpost extended (several inches) to put a good chill
on.
I performed the operation on a summer day when the air temperature in
the
garage was above 90.

Lastly, I really had tried everything else; oil, penetrating
lubricant,
gentle heating, strong twisting. *The frame builder suggested that I
return the frame and they would remove the seatpost with a torch,
check
the frame for trueness, and repaint it after severe heating. *I was at
the end when I thought of the dry ice technique.

The dry ice worked for me, and I still ride the bike.

Tom Noll

give it a go?

Cheers,

MD


Also shock chilling method which relies on the greater heat
conductivity of aluminium to contract faster than the steel. Heat up
with a torch (dont smoke the paint). Insert hot post into cold water
to boil off. When water stopped boiling, move post.
 




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