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Seatpost binder bolt unusual

Old 08-09-22, 03:50 PM
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Kars
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Seatpost binder bolt unusual

Has anyone ever seen this type of seatpost binder bolt? Can a different more standard one be used here ? There is no slit in the seat tube that can be clamped down on.Thanks in advance

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Old 08-09-22, 03:57 PM
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Don't use that with a carbon post. Obviously.
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Old 08-09-22, 04:34 PM
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Not unusual, notched side goes against the seat tube.
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Old 08-09-22, 05:03 PM
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Originally Posted by Crankycrank View Post
Not unusual, notched side goes against the seat tube.
does it clamp as well as a standard one? Sorry for my ignorance. All my bikes except this one have a bolt that squeezes down on the seat tube.
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Old 08-09-22, 06:25 PM
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Originally Posted by Kars View Post
does it clamp as well as a standard one?
I have only spoken to about two riders that have this setup and they said there were no problems. Make sure the seatpost is the correct size and, as mentioned, no CF posts.
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Old 08-09-22, 06:33 PM
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There are usually more than one reason why a design isn't used commonly. In this case the lesser ability to hold the post in place, compared to the usual slotted clamp design, is likely a big reason. Just look at the surface contact area of this design and look at a common slotted clamp and think about the huge difference. Less contact surface area means greater pressure will be needed for the same ability to hold the post.

This pinching internal binder has been done quite a few times over the bike industry's history. A well known version is the Fregus from the 1960s and 1970s. Try to find a replacement binder bolt set these days, oh and you better know which subtly different version your bike needs. Andy
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Old 08-10-22, 06:43 AM
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Looks like a Look to me. I have a Look 481sl that uses a binder bolt like that. The bike comes with a carbon seat post
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Old 08-10-22, 08:43 AM
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Originally Posted by alcjphil View Post
Looks like a Look to me. I have a Look 481sl that uses a binder bolt like that. The bike comes with a carbon seat post

I hope the carbon post has been designed with the pinching binder in mind. Carbon isn't best used when localized compressive forces are at play. Andy
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Old 08-10-22, 10:15 AM
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Originally Posted by Andrew R Stewart View Post
There are usually more than one reason why a design isn't used commonly. In this case the lesser ability to hold the post in place, compared to the usual slotted clamp design, is likely a big reason. Just look at the surface contact area of this design and look at a common slotted clamp and think about the huge difference. Less contact surface area means greater pressure will be needed for the same ability to hold the post.

This pinching internal binder has been done quite a few times over the bike industry's history. A well known version is the Fregus from the 1960s and 1970s. Try to find a replacement binder bolt set these days, oh and you better know which subtly different version your bike needs. Andy
I definately agree with you on that. I dont like this method and wish this bike just used a more common method but that being said I cannot change it and will only hope it continues to clamp properly. Also, a 27.2 mm post only went into the frame partially and had to push kind of hard. I tried a 27 mm and that went in nice and easy and so likely that is the correct size.
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Old 08-10-22, 10:17 AM
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Originally Posted by alcjphil View Post
Looks like a Look to me. I have a Look 481sl that uses a binder bolt like that. The bike comes with a carbon seat post
it's not a Look but that is interesting to know that Look did this also. Mine is a Carrera.
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Old 08-10-22, 10:19 AM
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In the few searches I did I could not find a replacement and so I guess I better not lose this bolt.
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Old 08-10-22, 01:25 PM
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This binder doesn't look too hard to make. A motivated person with basic metal working skills and tools (Tap, drill, file, hack saw) could do it. A machine shop would likely do it nicer and want more than a few dollars. If you're near Rochester, NY drop me a PM. Andy
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Old 08-10-22, 05:54 PM
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Originally Posted by Andrew R Stewart View Post
This binder doesn't look too hard to make. A motivated person with basic metal working skills and tools (Tap, drill, file, hack saw) could do it. A machine shop would likely do it nicer and want more than a few dollars. If you're near Rochester, NY drop me a PM. Andy
Thanks very much for the help. Not near Rochester but if I lose it I may call upon you for guidance. I wonder if the factory hand made this bolt because it looks kind of rough or maybe the previous owner made it.
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Old 08-10-22, 08:17 PM
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Please do who ever has to duplicate this binder and record the dimensions and take better photos for reference. Otherwise a fairly simple fab job turns into a bigger design and hope it works one. That bigger job will be best done with the frame in the hands of the fabber. Andy
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Old 08-11-22, 06:59 AM
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Originally Posted by Andrew R Stewart View Post
I hope the carbon post has been designed with the pinching binder in mind. Carbon isn't best used when localized compressive forces are at play. Andy
The seat post that came with the frame is a Look product. I have owned 3 Look frames that used the same seat post and binder bolt arrangement. I assume that Look knows what they are doing
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Old 08-11-22, 01:37 PM
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Originally Posted by alcjphil View Post
The seat post that came with the frame is a Look product. I have owned 3 Look frames that used the same seat post and binder bolt arrangement. I assume that Look knows what they are doing
Do you have a picture of that bolt ? Does it look (no pun intended)like the one I have or is completely different?I am not planning on using a carbon seatpost but am still curious.
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