mauin1x

I removed seized seat post from seat tube and now it is bent/twisted. It's also a curved or s-shape seat tube (not sure what correct name is) so only top part is bent/twisted. Any ideas on how to straighten it?
https://imgur.com/gallery/44sUVMI

wheelreason

The same you bent it in reverse?.....

soyabean

I'm quite the seat post is never supposed to slide past into the curved part of the seattube.

I'd do whatever you can to the seatpost if you want to save it. You won't make it any more worse, short of just tossing it for another.

I've found that city park cast iron fences very nice for bending things.

FBinNY 

Damn you, you.stole my answer!!

To the OP.

It sounds like we're being facetious, but the truth is that's basically it. Jig the frame up the same way, and use the same tools and force as before.

Bending or straightening frames is a creative art form and methods vary. I've saved frames by bridging them across supports, (telephone books) and stepping on the middle. So, since u ou creatively bent it, get creative and work it out.

mauin1x

the seat tube is what is bent not the seat post. And it is the top half closest to the seat post clamp that is bent if you can see that in the photo. The post isn't seized anymore, this happened as a result of getting seized seat post out

soyabean

I can't see anything in that bad photo, so I'm just guessing.

I would suggesting providing a side view of the whole bike, it's what bike folks are used to seeing.

mauin1x

Here is from side view its a curved seat tube so twist is hard to see. It twisted after I had to get a seized seat post out. And you can see in 1st photo that the built in seat clamp is off center from the twist

grumpus

Can't see any detail in those pictures, can barely see that it's a bike. Try putting the bike against a plain wall, with sunlight shining on it from behind you, close enough that it just fits in the frame. And the right way up - we like to see things the right way up, not upside down.

soyabean

I still have no idea what the OP is talking about.

If that ENTIRE seattube all the way to the bottom bracket is supposed to be straight (this looks like a GT), then the work is complete having parted out the bike and now the frame can be tossed for scrap.

Kontact 

Okay, the OP had a stuck seat post, and he got it loose by rotating the seatpost in the seat tube as you normally would. It sounds like the force of trying to twist the post free caused the upper part of the seat tube (probably above the seat stays) to either twist and/or bend.

This has nothing to do with the lower part of the seat tube being curved.

It likely happened because of the way the seat tube is connected to the top tube and chainstays several inches apart, and less than perfectly concentric forces.


I would agree that putting another post in, tightening the clamp down and twisting/bending in the opposite way that caused the problem might work. Use a good fitting post with no grease so the clamp doesn't have to work too hard. But it may not be possible to quite untweek this.

FBinNY 

IMO the force that would be needed to twist the tube here is beyond staggering. The tube is well constrained by the top tube, so we're talking about twisting noticeably over an inch or two. I suspect that the binder ears are where they've always been and the OP never noticed before.

OTOH, sideways bending is possible, so the OP could fixture the frame and use a square with a bubble level to localize the issue and proceed from there.

dsaul

I think the OP's problem is that the ear of the integrated seat post clamp is bent. I would think that just tightening the clamp would bent it back. If it's just the ear, he could probably remove the bolt and use an adjustable wrench to twist it back into position. If the whole upper part of the tube is pulled away, put the seat post in there and do some blacksmithing with a hammer and a block of wood to protect the paint.

freeranger

It seems like if the seatpost is actually twisted, that it would have broken a weld or caused more damage than just twisting the ears. If the top of the seatpost is still in line with the portion below the top tube, I'd be tempted just to use it as is. I wouldn't go trying to do more twisting-could make things worse. Any good frame builders in your area, who could take a look? Have you ridden it since to see if it still tracks straight? Looks like if the top of the seatpost is twisted that it would have been necessary to deform the top tube also (is it still straight?).

smd4

This.

FBinNY 

Back to the basics, and the first rule of mechanics --- identify and qualify any problem, before attempting to fix it.

I'll assume that there MAY be a bend just below where the seatstays join.

That's where it seems to be in the first photo, though it might simply be a result of the camera angle.

So, reiterating my earlier post, the OP has to start by verifying if there is a bend, then measure to find out where and by how much.

soyabean

As others have also said, OP needs to put in the effort to provide decent and proper pics if they want receive remote help.

It's really not that hard.

And better if they can edit to mark where they think a problem is, because I can do is guess and conclude that this frame is scrap.

Iride01 

If the new post slides up and down and the clamp holds it securely then what's the issue? It's a old bike. Is it just that the tube with the clamp appears twisted? Then that defect can become part of the character and charm of the bike. If anyone notices it can be a conversation starter. Possibly for a new friendship.

Like anything else, the area should be watched now and then for cracks. But to me, more damage will be done trying to twist it back into shape. Even if that's just more work hardening of the metal that causes it to crack later on in life. But sooner than if it'd been left alone.

Kontact 

It sounds like the top of the seat tube is no longer straight, so the saddle isn't going to be level laterally.

Duragrouch

The photo posted by someone else makes it a lot more clear; I thought there was a ton of seat tube sticking up, but that is just the tube above where the diagonal seatstays pass the seat tube on the way to the top tube. OK. Understanding the design, the seat tube is very triangulated fore/aft, so I doubt bent in that direction. Lateral bend is a different story, the seatstays are small diameter so less stiff in both bending and torsion where they attach to the seat tube, and, the whole tube loses a bit of lateral strength and stiffness due to the intentional curve to clear the rear tire. Steel being very forgiving, very small strain (stretch/deformation) so no work hardening, I think it should be able to be bent back no problem. Essential before starting to have a way to measure, if not by numbers, just eyeball, like a good and long straight-edge placed along the side of the seat tube and the same side of the top tube and extending to the side of the head tube and checking gap or interference there, then switching to the opposite side and comparing, or just eyeballing the seat tube directly for straightness, they used to straighten 1903-A3 Springfield gun barrels after turning that way, which is why the outside seems uneven when re-turning the outside to sporterize the rifle.

EDIT: The OP never claimed the frame is steel. It could be aluminum, which would be easier to yield in bending and torsion, especially since those tubes are not very oversize. Also, according to someone else's pic, it looks to be a track frame, so it may be built racer-light.

Iride01 

If that's the case, then I don't see it in the shorter straight portion of the tube above the stays. But possibly in the first picture the OP gave, when I import the pic and draw straight lines along the seat tube, the S-curve might have a twist in it.

However still what I'm seeing there could be the camera not being exactly on the centerline.

The only thing I can somewhat agree on is that the ears of the clamp seem to be just a tad pointed toward the drive side. Though that first pic does also make it looked like the ears of the clamp aren't quit lined up horizonatly. But the poor contrast is really hiding too much detail.

Kontact 

I'm not sure if the important function of the thread is to validate what the OP can see with his own two eyes. He says it is bent - why not just believe him and answer his question about bending it back?

FBinNY 

I agree in principle. However, I've seen too many examples of OPs poor judgement or explanations in identifying a problem.

Earlier, twisting is mentioned, based on the binder ears being off center, which is simply not possible.

This is why, iso often end up trying to get OPs to do proper diagnostics to identify the problem, before I jump in with helping fix what ain't broke.

Kontact 

Bending is also mentioned. If the little triangle formed between the binder, top tube at the stays and seat tube at the stays is tweaked off center (bending from the two stay contact points) that is going to look like the clamp is a tiny bit twisted because everything is off center. Which is completely "possible".

I sort of doubt there is a perfect way to photograph this with a single lens camera.

Anyway, if you don't believe anything is possible, then you probably don't have a solution. I just don't know why folks here believe the best way to help people is to harass them and imply they are liars - then instruct them to scrap the frame.

smd4

I think @FBinNY has been perfectly rational in his assessment, based on pretty poor photos. Certainly he hasn’t “harassed” anyone or implied anyone was lying.

Kontact 

I was speaking generally about the responses in this thread and threads like this in general. People talk to those requesting help like it is a scam or something.

Everyone doesn't know everything, but the people that come here looking for help have eyes and are being honest. A little more respect and a little less exasperation that problems aren't presented the "right way" would make this a much more useful and welcoming forum.