Bicycle Mechanics - Perplexing Colnago seatpost clamp

I cannot for the life of me figure out how to remove a seat from this very nifty but very perplexing Colnago seatpost. Anyone have a clue?

Unlike any seat post clamp I have ever seen, this one has an elegant almost one-piece claw that 95% surrounds the top clamp piece. Even with the bolt completely loosened (and even removed) I cannot figure out how to remove the clamp from the saddle rails.

It would appear that the top clamp piece would have to slide out sideways, but there is a little edge to it still grabbing the saddle rail that seems to prevent that.

anyone? anyone?

It's sort of a chinese box puzzle. I've never seen that post, but obviously there's a sequence of operations that will free the clamp.

Try rotating the seat and clamp to where the opening would be widest when loose, ie. with the two clamp elements on either side of the slot and see if that's enough to pop the smaller clamp sideways and free the saddle. If you need a bit more room, you can spread the post slightly, but the best way isn't to pry it, but to put the bolt into the threaded side and tighten it against a penny put into the slot.

I see you've beat this up quite a bit already, if you get totally frustrated and have no intention of using it again, you can always resort to a hacksaw to cut the front of the clamp off freeing the saddle and clamp elements.

Remove the saddle from the clamping parts.
Might work better if you take the post out of the bike first.
slide the seat forward and get 1 rail out first.
from the back where the rails bend wider.

or spread the rails till one comes out, sideways.

then once the saddle rails are out of the clamp, the parts will all pass thru the hole.

Looks beat up, I'd shop for another seatpost , or take the time
to file sand and polish all the marks out..

Looks to me like the clamp part on the top might hook under a lip on the front of the seat post and then is pulled down at the rear by that screw. Remove the screw and see if the clamp pivots forward. If it does, pivot the clamp forward and up until you can remove the top cylindrical piece or get the hook at the front to disengage from the seat post.

Thanks but sorry, I must not have been clear. the problem (in fact the only objective) is getting rails free (so I can swap the seat.)
I don't really want the parts out of the clamp.

But I see no way to get enough play to free up even one of the saddle rails.

and it is really quite a beautiful seatpost. I think the photos are exagerating the flaws.


Remove the saddle from the clamping parts.
Might work better if you take the post out of the bike first.
slide the seat forward and get 1 rail out first.
from the back where the rails bend wider.

then once the saddle rails are out of the clamp, the parts will all pass thru the hole.

Looks beat up, I'd shop for another seatpost ,or take the time
to file sand and polish all the marks out..

I'll post more and better pictures.

The surround is almost one complete piece. there is only a small 1/4" max gap that tightens up and grips the two clamp pieces when the bolt is tightened. But it doesn't seperate much at all when the bolt is loosened. It just loosens it's grip on the two clamp bits enough to reposition the angle of the saddle. But not enough to actually remove the saddle. At least not that I can see.

OK so I took another look at the pictures. As I said think of it as a Chinese puzzle box. I notice that one section of the post clamp area is sculpted narrower than the rest. 20:1 that's the key to the solution. Look very closely at the two clamp halves and see if any might have some relief so that if rotated to the narrower section would open wider.

Otherwise, consider that when loosened the opening is oval. Try rotating the saddle so the rails line up with the slot so the clamps can separate toward the widest part of the oval.

So far, you've been trying force, when the post wants finesse. Go have a beer and come back to it with an open mind looking for the trick (guaranty there is one) rather than using strength, and you have that V8 moment and have the saddle off. Like so many things it'll turn out to be very easy once you figure it out.

What happens if you push the saddle all the way forward? Can you push it past the bends in the seat rails? I'm wondering if the upper and lower side clamps won't pull out horizontally if you can get the seat far enough forward (probably past the bends). Another possibility, is there any way to remove the seat rails? (I can't see the back anchors in the photos).

Can you lift the nose of the saddle enough so that the rail clamps can be pushed off center?

"What happens if you push the saddle all the way forward?"

Pushing the clamp all the way forward or back doesn't seem to make any difference or show an obvious way of removing it.

Shame, I couldn't make the No Click Cycling Club monthly meeting last night. There would have been 10 or 15 bike collectors and I am sure that had I passed this puzzle around someone would have seen it before or been able to figure it out.

From the photo's it obvious that there's decent access for you to put the bolt in from the threaded side so you can use it to jack the post open a bit (put a penny in the slot for the bolt to push against) and maybe buy yourself the needed room to slip the clamp across. Have you tried that yet?

OTOH, the entire seatpost seems hopelessly beat up, so maybe you need to ask yourself if you ever plan on using it again. If it's headed for the scrap bin anyway, why not spare yourself the grief and remove the saddle with a hacksaw?

I swear I've seen something similar one time where there was a trick like you rotated it the right way and suddenly you were able to slide the top part of the clamp through the hole or something and then just lift the saddle off, but I can't remember what it was for the life of me and may in fact have dreamed the whole thing.

OTOH, the entire seatpost seems hopelessly beat up, so maybe you need to ask yourself if you ever plan on using it again. If it's headed for the scrap bin anyway, why not spare yourself the grief and remove the saddle with a hacksaw?

Again, the clamp portion is a little marred. I expect some previous owner got equally frustrated and got aggressive.
But, again, I think the photos are understating the condition.
The post tube itself is in very good condition, in fact unblemished and with no insertion marks.
And it IS a Colnago branded seat post (which alone is worth something).
And it IS certainly a "unique" design.

Maybe I should be fussier but several of the Campagnolo SPs I currently ride on myself are in far worse condition.

I don't mind hacksawing off the seat rails. Seats are a dime a dozen. but I do want to save the Seatpost and short of sticking it in a picture frame on the wall as a collectors item, I would like to figure out how the darn thing works (for the simple reason that I would like to reinstall it.)

When the bolt is out of there, is there enough room that you can flip the top part 180 degrees to the part usually touching the rails faces the underside of the seat? Then you might be able to slide it sideways a bit (maybe through the hole and completely out of there or maybe just enough that you can get it off one of the rails. I think that's how the thing I'm remembering worked.

but I do want to save the Seatpost and short of sticking it in a picture frame on the wall as a collectors item, I would like to figure out how the darn thing works (for the simple reason that I would like to reinstall it.)

OK, then take the advice I and others have given you and look for a finesse solution. The clamp won't yield to brute force, and even if it does,it won't be reusable. Some where in the allowable range of motion, is a position where there's enough room to either slide a part sideways, or spread them apart a bit more to free the saddle.

Also take a careful look at the 4 cradles. It could be that they're not identical, and one part may be slid either to the right or the left, but not either way. If you can't see any gateway, use the bolt and penny as a jack and spread the post slightly. This is how ttt stems were handled years ago, and a gentle spread won't hurt the post and might buy you the last bit of room that you need.

the advice I and others have given you and look for a finesse solution.

Absolutely, Finesse is the only way forward. Some genius designed this thing brilliantly. but just forgot that mere mortals would be using it and without a user's manual.

I have no shortage of seatposts. This is just a challenge and so there is no rush.

(They should hand one of these out as a Mensa qualifier.)

Maybe if you cut the rails just to get it out of there, looking at it from an installation standpoint might make more sense and pop on a light bulb as to how it works.

Also, could it have been made for a saddle with some sort of removable rails, and forced onto the present saddle by someone before you (hence the marks on the clamp)?

Do SAT tests even include Mechanical Logic questions these days?

these questions from and my answers to an engineering / cycling friend of mine

The seat post is pantographed "Colnago" (which, beyond the unusual design is what makes it interesting. And more valuable) also marked is "Ital Manumbra.." or something suggesting it is made in Italy. Certainly would have been made by 3TTT or ITM.

Objective is to remove the seat, Yes. Liberate the seatpost.
It's become more of an academic challenge than a practical one now. The seat and post combo is perfectly fine - I was just in the process of separating my seats and posts and got stumped on this one.

Loosening (or removing) the bolt releases some of the grip on the rails. Enough that I can reposition the seat back and forwards on the rails and adjust the tilt.

Bolt can be completely removed. not stripped, not jammed. That's not the problem.

Correct. Goal is to separate pillar and clamps from rails.
It is not stuck so much as I do not see anyway to loosen the grip enough to get it off the rails.

That one-piece top of the pillar almost completely encloses the clamps.

Clench your fingers into a half circle. Now bring your thumb to the middle finger. Now back that thumb tip off a quarter inch. That is what the top of the seatpost pillar looks like.
The two clamps are inside the the hole between you thumb and fingers.
The bolt runs from thumb to Middle finger.

tighten the bolt would close the gap but loosening it doesn't not open the gap up enough to do anything.

Weird.

On 22/03/2012 1:29 PM, Steve Kruse wrote:
>
> > You're a bright guy.
>
> A font of useless knowledge, to be sure.
>
> > obviously it would be easier if you had it in hand, but do you see any
> > obvious way to get this off?
>
> If the frame is Colnago, the seatpost itself is either
> Campy (most likely), Gipiemme (less likely) or maybe
> Shimano. Is the make of seatpost non-obvious ? I
> doubt the make is Laprade or SR or some knock-off.
>
> The problem, as far as I can deduce, is that you un-did
> the seatpost bolt yet the clamp did not get loose and
> so the rails of the saddle still are locked in place. Is
> that correct ? When you say "get this off" your aim
> is to remove the saddle from the seatpost, except
> everything is still as if the bolt was still tight ?
>
> Or is the head of the bolt (recessed hex) stripped ?
>
> Or is it that, regardless of the saddle, your aim is
> to separate the pillar of the seatpost from the rails
> and clamp at the top of the pillar, but it's stuck ?
>
> Looked at the photos but didn't say Aha! yet.
>
>
>
>

Nitto made a nice nickel plated steel pry bar for their stems ..
the idea is to spread the slot, enough to slip a rail out of the clamp..

If you cannot get the thing pried open enough to get the saddle out ,
set it aside and get one of your other seatposts and saddles and go for a ride .

If you cannot fix it, then you cannot. .. accept that go on with your life

What happens if you twist the saddle? (pushing the nose to the right and the back to the left for example). Would the seat rails pry out of the clamps? You might need to mount the seatpost in a frame to get some leverage. (I'm sure if you did it hard enough it would work, but that's not really the point.)

Can you see inside the hole between the upper and lower clamps? Is there anything unusual there that might be the key?

Are the upper and lower clamps 1 piece each? Basically, are there 2 pieces here, or 4? You should be able to tell, but it wasn't exactly clear in the photos.

So what's the problem?

Looks to me you should completely remove the bolt. Then lift and rotate the upper portion of the clamp 90 deg. Remove saddle.

Reverse steps to re install.

So what's the problem?

Looks to me you should completely remove the bolt. Then lift and rotate the upper portion of the clamp 90 deg. Remove saddle.

Reverse steps to re install.

Can't do that. It's a type of 2 piece clamp in which one piece is captive within the other. It doesn't loosen up enough to get the rails out. If what fietsbob says above is correct (about there being pry bars for these types of stems), then that might be what needs to be done.

Pstock, post this on Classic and vintage, one of the regulars on there will have seen this type of post before and be able to advise.

It's a type of 2 piece clamp in which one piece is captive within the other.

actually the two clamp pieces - top and bottom - are captive within this one-piece jaw mechanism. Having stared at it for days now, I now see it like a brontosaurus holding two pieces in its jaws.

I think that the two halves that clamp the seat rails when the bolt is loosened, the top half can be pushed out to the side and the seat can be pulled off one of the rails. You may even be able to push the upper half all the way out and just lift off the saddle.

Thanks to Olivier Alonzo here in Toronto for solving this puzzle.
(though frankly it was not fair to everyone else that you did not have the assembly in your hands for inspection.)
Olivier did (one evening at a recent Toronto NoClick Cycling Club meeting) and noticed what should have been obvious - that the bottom clamp had a split in it.

The bottom clamp was in fact two pieces and, with a bit of a bang, the Left and Right sides of the lower clamp slid out allowing the whole mechanism to be disassembled.

again, should have been obvious. since the main post could not be forced open, that either the upper or lower clamp had to move.
But still, in the dozens of seatposts I have dealt with, some with some goofy designs, I have never seen anything like this ITM one.

Thanks Olivier. Thanks to you all.

Peter

I think that the two halves that clamp the seat rails when the bolt is loosened, the top half can be pushed out to the side and the seat can be pulled off one of the rails. You may even be able to push the upper half all the way out and just lift off the saddle.

close. it's the bottom half that is split and slides out.

Very interesting, thank you for documenting this.

Thanks to Olivier Alonzo here in Toronto for solving this puzzle.


I first described thus as a Chinese Puzzle Box, and that's what it turned out to be. Thanks for posting the solution.

If the clamp that is welded to the post is a circle, I'd feel a lot more confident sitting down if I reassembled it with the split half on top.

If the clamp that is welded to the post is a circle, I'd feel a lot more confident sitting down if I reassembled it with the split half on top.

Unless there was another factor, I'd probably do the same. But if you think about it, once the clamp is tightened, there's no possibility of the segments camming out. There's no place for them to move, so it probably doesn't matter either way. Still, one piece section on the bottom, kind of a belt and suspenders approach.

If the clamp that is welded to the post is a circle, I'd feel a lot more confident sitting down if I reassembled it with the split half on top.

All of my seatposts with different size clamping jaws have the larger jaw on the bottom. It also may not be possible to assemble it upside down if the seat has a skirt.

Unless there was another factor, I'd probably do the same. But if you think about it, once the clamp is tightened, there's no possibility of the segments camming out. There's no place for them to move, so it probably doesn't matter either way. Still, one piece section on the bottom, kind of a belt and suspenders approach.

Agreed it would most likely make no difference, but I find the more nagging doubts I can silence, the more I enjoy a bicycle.

OP, sorry to plant this seed of doubt if you can't flip the clamp parts.

Unless there was another factor, I'd probably do the same. But if you think about it, once the clamp is tightened, there's no possibility of the segments camming out. There's no place for them to move, so it probably doesn't matter either way. Still, one piece section on the bottom, kind of a belt and suspenders approach.

The top bit is marked "Supra" which I believe means "Up" and so suggests that the longer bit goes on top, and the two split bits go on the bottom. But, it might still be bad design.

OP, sorry to plant this seed of doubt if you can't flip the clamp parts.

I'll try flipping it and see what happens.
But in the end it might be a moot point because the other oddity is that the diameter of the post is 30mm and doesn't fit any bike I have personally.
I have no clue which of the dozens of bikes I have handled in the last 2 years it comes from (seatposts were often removed for shipping and storage or swapped around to period issues). It presumably came from a Colnago.
But all four Colnagos I have handled have gone out the door with seatposts, and none of them took (as far as I recall) a 30mm seatpost.
(Maybe it was that C40 carbon job that I parted out and sold as frame only.... hmmm.)

The top bit is marked "Supra" which I believe means "Up" and so suggests that the longer bit goes on top, and the two split bits go on the bottom. But, it might still be bad design.

As I said, once clamped the parts have no place to move. People get along perfectly fine with either belts or suspenders, so "bad design" is unfair. I might have done things differently, but the manufacturer probably had their reasons, possibly as simple as better access for sliding out the removable parts.

Indeed, it was that C40.

Maybe I shouldn't have knocked it down. (But it looked awful retrofitted with a long reach Alivio rear derailleur.)