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Singlespeed & Fixed Gear "I still feel that variable gears are only for people over forty-five. Isn't it better to triumph by the strength of your muscles than by the artifice of a derailer? We are getting soft...As for me, give me a fixed gear!"-- Henri Desgrange (31 January 1865 - 16 August 1940)

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Old 04-20-11, 05:59 PM   #1
illdthedj
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bianchi pista concept seatpost clamp question...

why hello there...

i have a bianchi pista concept. (its my grocery getter)

i have heard the horror stories about the integrated seat post clamp cracking from over tightening...

luckily the concept frame i bought from my friend is free of that issue, and i havn't cracked it myself (yet).


just some questions about this integrated seat post clamp:
1) im guessing to be super precise and be absolutely careful not to over tighten and crack it, you would need a torque hex wrench? anyone know the torque limit? or a good/cheap torque wrench?
2) theoretically speaking, is a cracked internal seatpost clamp fixable? or are you SOL?
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Old 04-20-11, 06:12 PM   #2
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FSA has a product that is made to be used on carbon fiber components/frames in place of grease to stop slippage and prevent the risk of overtightening but I've found it to work exceptionally well on aluminum too. I used it on my Leader and didn't need to tighten the seatpost clamp nearly as much as I would have without it.

http://www.jensonusa.com/store/product/CM407B09-Fsa+Carbon+Seatpost+Installation+Compoun.aspx

Finish Line makes a comparable product as well called Fiber Grip but it's a little more gritty than the FSA stuff.
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Old 04-20-11, 06:15 PM   #3
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Quote:
Originally Posted by illdthedj View Post
i have heard the horror stories about the integrated seat post clamp cracking from over tightening...
It's mostly a problem with 2005 and earlier Concepts, so if yours is a 2006 or later I wouldn't worry about it. If your seatpost is a good snug fit, you don't need to tighten it a lot. I just tighten mine enough so that I can't twist the seatpost when I grip the saddle and try to turn it. I'd ride it around the block a few times and make sure it doesn't slip down when you sit on it.
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Old 04-20-11, 07:08 PM   #4
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i dont think i have a solution to it but my structural engineering degree and license tells me it should help:

i tie rubber bands around the collar to compress the area that will be put in tension if you tighten the bolt, so that the uniformally radial compression force can in theory reinforce the tensile force of the clamping done by the bolt because it acts against it.
*IN THEORY* it helps. in practice? not enough data to support any hypothesis. but, i have not cracked anything. also im not heavy @170lbs so the bolt doesnt require as much tightening as maybe other guys who weigh 200lbs

*DISCLAIMER: rubberbands deform and crack. replace at least once every 6 months.

p.s. vegetable rubberbands (the one at safeway) work the best: no sticky and they're thick enough.


TL : DR, i wrapp rubberbands around the collar to anti the clamping outward force
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Old 04-21-11, 11:09 PM   #5
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I just had this happen to me about a month ago. I've retired the bicycle in hopes of saving my dream bike.

I plan on drilling the hole to stop the crack, but other than that repair is a ***** and usually will result in the bike being damaged again.
If it happens, make sure you stop it ASAP. Even if I can't keep mine, it's going to be a decor item (;
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Old 04-22-11, 12:02 AM   #6
cc700
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Originally Posted by muckymucky View Post
i dont think i have a solution to it but my structural engineering degree and license tells me it should help:

i tie rubber bands around the collar to compress the area that will be put in tension if you tighten the bolt, so that the uniformally radial compression force can in theory reinforce the tensile force of the clamping done by the bolt because it acts against it.
*IN THEORY* it helps. in practice? not enough data to support any hypothesis. but, i have not cracked anything. also im not heavy @170lbs so the bolt doesnt require as much tightening as maybe other guys who weigh 200lbs

*DISCLAIMER: rubberbands deform and crack. replace at least once every 6 months.

p.s. vegetable rubberbands (the one at safeway) work the best: no sticky and they're thick enough.


TL : DR, i wrapp rubberbands around the collar to anti the clamping outward force
skepticism: i haz it


(seriously, the rubber bands probably only push in a fraction of the tension pushing out, and not a good fraction either.)

i greased the **** out of my visp (same mechanism) and it stopped creaking. also, poor design is poor design. what?
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Old 04-22-11, 12:24 AM   #7
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Hmm this has never been a problem for me, for my pista concept or 727 who has integrated clamps and grease is what I use... it helps to condition the clamp every now and then through by removing the seatpost and tightening and then loosening the seatpost clamp.
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