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Seatpost bolt/clamp for 23.4mm seatpost?

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Seatpost bolt/clamp for 23.4mm seatpost?

Old 08-23-13, 09:29 PM
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Curiouswill
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Seatpost bolt/clamp for 23.4mm seatpost?

Hi, everyone. I have been trying to figure out the info needed to replace my seatpost bolt. As you can see in the linked image below, I really need to replace it. However, I do not know whether I can simply get the next size up clamp and simply overtighten it to fit. I am not able to find out if I must use strictly the right size clamp on this or if I only need the approximate sized one. I don't want to waste money trying this out only to end up with the same result so here I am, asking for advice regarding this.

Thank you

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Old 08-23-13, 10:11 PM
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You may be SOL. The clamping ears are part of the frame, and are collapsed and touching in back. This usually happens because of overtightening.

If the structure is still reasonably OK (the left side doesn't look it) you might be able to get more ability to clamp by filing from the inside of the eats so they can close farther. OTOH since the ear is already collapsed, there's a better then even chance that the ear will simply collapse more.

The normal fix for this is to bend the ear back to the correct shape, fill it with braze for structure, then re-drill the bolthole. That's not a cheap job, and probably much more than this frame is worth.

OTOH, if you just want to keep this alive until you can get something better, here's the down and dirty fix.

1- set the saddle to the right height and pointing forward. Get this right because this is it, and will never change.
2- drill an hole straight across the seat tube just below the lug, going through the post and out the other side.
3- run a bolt through and tighten until the tube ovalizes just slightly.
4- clean up the bolt and nut by filing off corners and edges.
5- run a bolt and nut through the ears, and tighten as best you can, and saw/file off any excess length.

Total cost = a few dollars and less than an hour of your time. Won't look good, but will work OK for a while.
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Old 08-23-13, 10:34 PM
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The clamping ear portion does not look like part of the frame. Here is a pic of it from above.

As you can see, there are 2 layer of metal. The clamp is stuck to the frame by the way of paint or possibly glue but it seem like I could remove the clamp and then clean up the area for a new better clamp.



Any suggestion of what to do about this?

thanks
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Old 08-24-13, 06:34 AM
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If you can indeed remove the clamp part, either by removing it if it is glued on as you suspect, or by grinding it off if it is brazed on as I suspect, you should be able to fit a collar-type of clamp which would be sized to the OD of the seat tube. You may be able to just grind off the ears, make the remainder as round as you can and size a collar to fit that OD.
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Old 08-24-13, 07:17 AM
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I've seen many of these cheap seat post clamps that were tack welded in place. I strongly doubt glue is in play and paint would mean assembly when wet. Not exactly what a high volume low cost manufacturer would tend to do. Francis's through bolt idea is the likely outcome. I do this on low cost unicycles often. Andy.
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Old 08-24-13, 07:52 AM
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Originally Posted by dsbrantjr View Post
You may be able to just grind off the ears, make the remainder as round as you can and size a collar to fit that OD.
Would I need a shim on the section where I would remove the ear to fit the newer collar? what kind of material could I use as a shim there while interfering with the clamp?
I measured it roughly and it does seem that this method allow me the most flexibility on the choice of collars to put there.

thanks
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Old 08-24-13, 08:12 AM
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Originally Posted by dsbrantjr View Post
If you can indeed remove the clamp part, either by removing it if it is glued on as you suspect, or by grinding it off if it is brazed on as I suspect, you should be able to fit a collar-type of clamp which would be sized to the OD of the seat tube. You may be able to just grind off the ears, make the remainder as round as you can and size a collar to fit that OD.
This isn't an option because it's part of the seat lug, or welded on, but in either case the seat tube doesn't extend above the top tube, so there's no place to put a collar.
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Old 08-24-13, 08:25 AM
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Originally Posted by Curiouswill View Post
The clamping ear portion does not look like part of the frame. Here is a pic of it from above.

As you can see, there are 2 layer of metal. The clamp is stuck to the frame by the way of paint or possibly glue but it seem like I could remove the clamp and then clean up the area for a new better clamp.
The ears are of one piece with the seat lug, the reinforcing band around the top or the seat tube, which forms the joint with the top tube (cross bar). There's ne extension of the tube above the top tube, so one look and 2 minute's thought will show you that there's no way to remove the existing "band" not a way to fir another.

I've repaired many of these as described in my first post, but that's not a cheap repair. You might get some ability for the ears to close mire by filing the inside of the back corners, but once they start collapsing, they don't stop.

If you want to try a DIY repair that might work, before going my last ditch route. Use some JB Weld, or comparable product to fill the ears, so they're less likely to collapse. JB Weld isn't super strong, but packed in the hollow box ears might be enough to prevent the sides from buckling. Clean the ears with acetone first (not nail polish remover) so you get a good bond. build it the fill in layers so it can cure well, allowing 24 hours between layers. Then drill it and cross your fingers.

To reduce the amount of hold needed from the clamp, consider either a traction compound such as carbon assembly paste, or even T-242 (blue) Loctite.

That might do the job, and you always have the last ditch if not.
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Old 08-24-13, 08:33 AM
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My sense is it should have looked like 1 filled brazed seam , but the brass did not flow between the parts, adequately,

but was painted and shipped, anyhow .. the prying the ears back out and separated the joint, more..

Will still hold the seatpost.. (?)


If you want to also repaint the frame, in part, or entirely.. the seam could be brazed in to fill the gap..

I question if the seatpost used was undersized, to make best fit , perhaps a next size up

that may be 0.2mm oversize Now but

use an adjustable reamer to hone the frame bore so the new post Just barely Fits and then stop reaming .


then there will be minimum compression force, needed, around the post by the frame.. but post wont slip.

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Old 08-24-13, 09:26 AM
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Originally Posted by FBinNY View Post
This isn't an option because it's part of the seat lug, or welded on, but in either case the seat tube doesn't extend above the top tube, so there's no place to put a collar.
Okay, I thought that there was some thin collar that I could use to fit onto the existing tube. Guess I'll have to switch to the DIY option like you mentioned below.

Originally Posted by FBinNY View Post
The ears are of one piece with the seat lug, the reinforcing band around the top or the seat tube, which forms the joint with the top tube (cross bar). There's no extension of the tube above the top tube, so one look and 2 minute's thought will show you that there's no way to remove the existing "band" not a way to fir another.

I've repaired many of these as described in my first post, but that's not a cheap repair. You might get some ability for the ears to close mire by filing the inside of the back corners, but once they start collapsing, they don't stop.

If you want to try a DIY repair that might work, before going my last ditch route. Use some JB Weld, or comparable product to fill the ears, so they're less likely to collapse. JB Weld isn't super strong, but packed in the hollow box ears might be enough to prevent the sides from buckling. Clean the ears with acetone first (not nail polish remover) so you get a good bond. build it the fill in layers so it can cure well, allowing 24 hours between layers. Then drill it and cross your fingers.

To reduce the amount of hold needed from the clamp, consider either a traction compound such as carbon assembly paste, or even T-242 (blue) Loctite.

That might do the job, and you always have the last ditch if not.
Thank you for the suggestion. I was thinking of something like this. Suppose I put a small washer or nut on the inside and fill the space between this and the ear with JB weld, would that work? Theoretically, this should allow me to use stronger material to fill the bulk of the empty space and then fill in the remainder of the space around the outside of the nut but within the ear more cheaply. Is this sound?

thank you for your advices
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Old 08-24-13, 10:42 AM
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Originally Posted by Curiouswill View Post

...Thank you for the suggestion. I was thinking of something like this. Suppose I put a small washer or nut on the inside and fill the space between this and the ear with JB weld, would that work? Theoretically, this should allow me to use stronger material to fill the bulk of the empty space and then fill in the remainder of the space around the outside of the nut but within the ear more cheaply. Is this sound?

thank you for your advices
Yes, a nut, drilled out, then filed to fit with JB Weld only as a gap filler would offer more structure than JB Weld alone. The strength still comes from the ears themselves, what your doing is supporting the walls so they can't buckle. If I remember it was the lower wall of the left ear that seemed to be most compromised, so make sure it's well supported.
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