Thread started by User1 at 12.14.08 - 5:28 pm

I forgot who it was that I was talking to that wanted to know how to unfreeze a frozen seat post. So hopefully it's someone that reads the posts. Here's what one frame builder suggested to me.


As for your stuck seat post, (Correct size is 27.2 mm.) this is a common occurrence. Aluminum and steel react together with the presence of water and corrode together as if they were welded. First, take the bike or frame outside and pour a pan of boiling water over the seat post. This will expand the aluminum, and initially make it tighter than ever, but when it cools completely it contracts, and this is often enough to break the seal.

If this fails, ammonia will remove aluminum corrosion. Turn the fame upside down and pour ammonia inside the seat tube, through the Bottom Bracket. Allow it to soak over night. You will need a saddle attached to the seat post for leverage, and hold the bike or frame between your knees as you twist back and forth.

As prevention is better than a cure; always keep the inside of your seat tube and the seat post smeared with grease. The same goes for an aluminum stem. Remove, re-grease, and replace at least once a year. More often if you ride in the rain a lot.

Anyone care to share any other tips?

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Put the seatpost in a vise and use the frame for leverage to take it out.



sc_nomad
12.14.08 - 5:34 pm

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http://sheldonbrown.com/stuck-seatposts.html

15 Ways To Unstick a Seatpost
Sheldon Brown photo
by Sheldon "Unggggghhh!" Brown
Removing a seatpost which is stuck in a frame can be one of the most
difficult and challenging jobs that may come your way.
These 15 tips should help you meet this challenge, and emerge victorious.

Prevention
To update an old saying, 28 grams of prevention are worth 454 grams of cure. Stuck seatposts are always the result of improper installation. If you do it right, you will never have a seatpost get stuck after you install it.

1. Always use grease. The inside of the seat tube should be heavily coated with grease all the way 'round before you install the seatpost. If you use enough grease in the seat tube, there is no need to grease the seatpost itself. (When you make a peanut butter sandwich, you only need to put the peanut butter on one of the slices of bread.)

2. The three rules of hammering seatposts:

1. Never install a seatpost with a hammer.

2. Never, never install a seatpost with a hammer.

3. Never, never, EVER install a seatpost with a hammer!

4. Do not install a plain "pipe-type" seatpost without having a saddle attached to it. They can slip down too far and get stuck where you can't reach them

Diagnosis
Before you get serious about a stuck seatpost, you should find why it is stuck. There are two possible reasons: The seatpost may be stuck mechanically, for instance by being the wrong size and having been forced in; or, the problem may be chemical, caused by corrosion.

5. If an oversized seatpost was forced into the frame, it will often make a noticeable bulge in the seat tube. Even if you cannot see this bulge, you can sometimes feel it by running your fingers up and down the seat tube about where you would expect the seat post to end.

6. If a thin-walled seatpost has been deformed (out-of-round) by overtightening the seatpost bolt, this will usually be visible where the seatpost emerges from the seat tube. If the seatpost is out-of-round, you should not expect to be able to get it to turn more than a few degrees from side-to-side. If you force it too far rotationally, you may jam it in even worse.

Cure
7. Do not try to remove a seatpost by pulling on it with a pipe wrench, locking pliers or any other tool. Instead, use a saddle. Nothing gets as good a grip on a seatpost as a saddle, because it has the hardware designed specifically for the purpose. If you are worried about damaging the customer's saddle, use one of the yellow BMX saddles you have in the cellar that will never sell anyway.

8. At the first sign of difficulty in moving a seatpost, remove the seatpost bolt completely, don't just loosen it. Sometimes this is all that it will take.

9. The next thing to try is prying the ears of seat lug apart slightly with a screwdriver. Sometimes it is easiest to stick a flat-bladed screwdriver between the ears and twist gently. Other times you may have better luck by inserting a large Phillips head screwdriver or Allen wrench into the bolt hole on one ear at a time and bending the two sides individually.

10. Most repairs are easier if the bike is held in a work stand, and for some jobs it is helpful to have the bike partially disassembled. This is not the case with seatpost extraction.

It is easiest to work with a fully assembled bike, sitting on the floor on its own tires. When pulling on the seatpost, the best way to hold the bike down is to put a foot on a pedal.

You can get the best purchase by standing behind the saddle, with your legs straddling the rear wheel. It may be helpful to have an assistant hold the front end of the bike steady. Even if you don't use an assistant, the front wheel should be restrained from turning from side-to-side. This may be done with a commercial handlebar clamping tool, or by strapping the wheel against the down tube with a toe strap.

For the most recalcitrant cases, if the seatpost has a one-piece saddle clamp, you can mount the top of the seatpost in a vise, then twist and pull the bike or frame. If you have an assistant handy, have one of you apply the force in a rotational direction, while the other applies force to pull the frame away from the seatpost.

Unfortunately, many seatposts will not lend themselves to this approach, because the saddle clamp may be pressed or bonded to the tubular part of the seatpost, and the joint isn't designed to withstand such force.
11. Normally, it is best to raise and lower seatposts straight up or down, without twisting them, because twisting can cause unsightly scratches on the seatpost. This does not apply when you are dealing with badly stuck post, however. With stuck seatposts, your first priority should be to try to turn the seatpost, even if it won't move vertically. You can apply much more effective force rotationally than you can vertically, and if you can get the post to turn, victory is in sight. Once you can turn the seatpost, you can run oil in between it and the seat tube, and the twisting action will distribute the oil, completely freeing the post.

12. For steel seatposts stuck into steel frames, where the problem is often caused by rust, penetrating oil can do wonders. If you don't have real penetrating oil, any light lubricating oil is better than nothing, but penetrating oil is made specifically for this purpose, and you should buy a can if you don't already have one.

13. Aluminum seatposts frequently become stuck by corrosion also, and penetrating oil is almost useless against aluminum oxide. Fortunately, aluminum oxide can be dissolved like magic by using ammonia.

14. If nothing else works to free up a steel or titanium seatpost, the next-to-last resort is to heat the seat tube up with a hair dryer or propane torch. This should be done with great care so as not to do too much damage to the paint. You should work as fast as you safely can, because you want to heat the seat tube so that it will expand, but if possible you should quickly put the torch down and start pulling on the saddle before the heat works its way through the seat tube and makes the seatpost expand too.

15. The torch technique is worse than useless when you are dealing with an aluminum seatpost stuck in a steel or titanium frame, because aluminum expands twice as much as steel, and 2 1/2 times as much as titanium for the same increase in temperature. In fact, the exact opposite technique will often do the trick for aluminum seatposts--cool the seatpost down as rapidly as possible. The contents of a CO2 tire inflation cartridge applied inside the seatpost can shrink it down just enough to do the trick.

16. If nothing else works, the final resort is the old hacksaw blade trick. Cut the seatpost off so that about 1/2" is left sticking out, then insert a hacksaw blade into the seatpost and carefully cut a slit in the post. This is very laborious, and you run the risk of damaging the frame if you cut too far, but this approach cannot fail. Once you have cut the slit, grab one edge of the cut with a locking plier and roll the seatpost up inside itself and pull it out.



JB
12.14.08 - 9:19 pm

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HSB



imachynna
12.14.08 - 9:23 pm

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Looks like PB Blaster is suggested alot in the bikeforum too.



User1
12.14.08 - 11:25 pm

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