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Seat post tube of frame is out of round

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Seat post tube of frame is out of round

Old 02-12-18, 06:57 PM
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albako
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Seat post tube of frame is out of round

Any simple way to get the tube fairly round again, slightly crushed.
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Old 02-12-18, 07:00 PM
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Seat post tube of frame is out of round

Any simple way to get the tube fairly round again, slightly crushed.
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Old 02-12-18, 08:38 PM
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cb400bill
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Duplicate threads merged.
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Old 02-12-18, 10:52 PM
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Originally Posted by albako View Post
Any simple way to get the tube fairly round again, slightly crushed.
It would be helpful to know what kind of material the frame is made of, and where the crushed section is.
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Old 02-12-18, 11:17 PM
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CliffordK
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Also, what size of seatpost?

i'm seeing a bunch of 1 1/8" muffler tubing expanders that likely would work for OS tubing, but not for 27.2.
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Old 02-12-18, 11:55 PM
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3alarmer
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...it's remarkable how difficult it is to successfully expand steel bicycle tubing to perfectly round once it's been ovalized.

Mostly the problem is getting it to go out past the point of elsasticity in the direction you want it to go, and if you don't do that, it snaps back to where it was or close to it. If you're just talking about the top, where the post insertion happens, you can sometimes just brute force a seat post to where you need it in terms of height, clamp it down, and use the bike.

In general, the cheaper the bike (lesser steel alloys are easier to manipulate), the more likely you'll have some success with this.

If it's just a cosmetic thing, and the post still works (like maybe it was still in the tube when it got squashed), the bike will probably still ride fine for a good long while.
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Old 02-13-18, 02:13 PM
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heavy steel accurately machined steel rod?
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Old 02-13-18, 02:29 PM
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Originally Posted by 3alarmer View Post
.
...it's remarkable how difficult it is to successfully expand steel bicycle tubing to perfectly round once it's been ovalized.

Mostly the problem is getting it to go out past the point of elsasticity in the direction you want it to go, and if you don't do that, it snaps back to where it was or close to it. If you're just talking about the top, where the post insertion happens, you can sometimes just brute force a seat post to where you need it in terms of height, clamp it down, and use the bike.

In general, the cheaper the bike (lesser steel alloys are easier to manipulate), the more likely you'll have some success with this.

If it's just a cosmetic thing, and the post still works (like maybe it was still in the tube when it got squashed), the bike will probably still ride fine for a good long while.
Yeah, it seems like you would something oval so the low spots could be pushed out past their elastic limit while leaving room for the rest of the tube to flex in, lest you just swage the whole thing larger.

If it was the top of the tube, I'd be inclined to try an undersized hardwood dowel that is split, then drive a wood wedge into the split. If (when) it gets stuck you just bore out the wedge.


But I have never heard of a tool for this.
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