# The Arcobaleno seat post bolt mystery.



## anjpp (Nov 4, 2009)

Just bought myself a beautiful Arcobaleno for small money - and was super happy until I understood why the seller probably sold it to me for so cheap. Since this is about a rare frame, I hope to find someone who has actually owned one of these beauties and can help me with first-hand experience...
The Arcobaleno (and the OV Pro as well, I think) have this strange seat post binder system where the bold is _in front _of the seat post in the top tube, see here for an example picture: https://farm6.staticflickr.com/5135/5428331088_8acf3caa8b_o.jpg. The strange thing is now that I just got a loose bolt with the frame, and there is no way to get the seat post sit tight in the frame with just sticking that bolt into the frame and then inserting the post. 
My suspicion is now that the (threaded) end of the bolt, kind of the nut, is supposed to be attached to the inside of the top tube wall and was ripped off by the previous owner (without informing me of the damage). 
My questions therefore are:

is my assumption correct, is the screw visible on the photo supposed to be screwed into the frame?
in case that's the case and the 'nut' has been ripped off of the inner top tube wall - any chance I can get this repaired? Or is it a hopeless case and not worth the trouble? 
Great thanks in advance for some Merckx owner knowledge sharing!


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## HigherGround (Mar 3, 2005)

I've never owned a Merckx with this arrangement, so I can't comment directly. However, if there aren't any useful responses here, you might try contacting Gita, the Merckx importer and distributor to the US. (I am assuming you're in the US, of course.) Good luck, that teaser pic looks great!


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## waydownsouth (Dec 30, 2006)

I've got one of these frames but it's at the other end of the country so I'm going to have to rely on my memory to explain this. As I recall there's a small horizontal tube thats brazed into the top tube immediately in front of the seat tube which contains the binder. This small tube is open at the back into the seat tube. The binder itself is made up of two halves (and the bolt), one of which is threaded. These two halves are shaped to match the diameter of the seatpost. The two halves of the binder are restrained inside the small horizontal tube and therefore when they are pinched together by tightening the bolt they push the seatpost backwards and hold it firm in the frame.

When I got my frame one of the halves of the binder was seized inside the frame so I had to punch it out and clean everything up before I could adjust my seat height but since I did this it's worked just fine. I would suggest that you use a seatpost with a reasonably thick wall (and certainly not carbon) as the binder exerts quite a lot of clamping force over a very small area.

As stated above I'm relying on my memory so when I'm reunited with the frame in a couple of weeks time I'll have a really good look at it and report back, but I think that assuming you've got all the parts (frame, bolt and two halves of the binder) you should be able to make it work. I'm pretty sure that the threaded half of the binder does not need to be fixed inside the tube as it will be held in place when tightened by the seatpost. I hope this helps, my apologies if my explanation doesn't make sense!


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## anjpp (Nov 4, 2009)

@HigherGround - many thanks, much appreciated info! I'm actually a German living in Singapore, so I think in case I cannot figure this out myself, I'll get in touch with Merckx in Belgium directly. 

@waydownsouth - I cannot thank you enough for taking the time to type this. What you write makes perfect sense and helps me a lot... I do have the bolt and two halves of the binder, but the reason why the solution does not work anymore seems to be that the threaded half's thread is almost completely gone and the former owners seem to have been trying to solve this problem by just adding a nut at the end. Unfortunately, this does not quite work.  So I think the only solution is for me to have a replacement machined, already connected with a few local bike builders and they might be able to do this for me. 
Just to clarify - in my frame, there is just a hole in the drive side top tube of the frame and a circular space cut into the top tube wall opposite that hole - I don't have the 'small tube' that you describe. Do you think I need this small tube remade as well or will the binder hold in place without that tube?
Again: massive thanks, I feel a bit closer to actually riding that gorgeous frame now. Many thanks for the hint re the seat post, will keep that in mind!


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## waydownsouth (Dec 30, 2006)

anjpp said:


> Just to clarify - in my frame, there is just a hole in the drive side top tube of the frame and a circular space cut into the top tube wall opposite that hole - I don't have the 'small tube' that you describe. Do you think I need this small tube remade as well or will the binder hold in place without that tube?


Upon further reflection I think my frame is exactly the same as yours. I think the small tube is probably a figment of my imagination, it's really just as hole in the top tube as you describe (it's been at least 2 or 3 years since I pulled mine apart). I will definitely check and report back when I get a chance to have a look at the bike (I'm in Auckland and the bike is in Christchurch at the other end of New Zealand). I wouldn't be surprised if your problem is simply that the thread in the non-drive side part of the binder is bad. I can imagine that the former owners solution of the nut and maybe a slightly longer bolt would sort of work, but not very well. I would imagine that you could find somebody to machine a replacement non drive side threaded binder part. I'll definitely take mine apart and post some photos of all the parts as soon as I get a chance.


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## pie (Jun 19, 2006)

I also own such a fantastic frame, had fantasic rides on it
until the seatpost bolt crashed.

My lbs couldn't help me and at the Merckx factory there were no spare parts available.

So i contacted a friend, his dad fabricated a new screw and bolt for my frame.	

I interested, I could send you some pics of it.

good luck!


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