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Old 03-12-11, 02:27 AM   #1
Squirrelli
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Seatpost Conundrum

I would love to hear you guys' opinion on this situation with my seatpost and frame.

I've got a C-Record look-alike aero seatpost by the company of Forginal? from Spain:


The minimum insertion mark is exactly 63.5 mm away from the bottom of the post. I have this post in my IRO Mark V frame:



The minimum insertion mark is about ~1mm on top of the seat tube and it is in there more than half way past the top tube.

My question is; since the top tube junction and top of my seat tube is quite the distance away, should I be worrying about cracking the seat tube of my frame? I am about 175lbs if it helps. (I'm a hefty squirrel.)
Am I just being overly paranoid about 1mm?

Thanks a lot guys!
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Old 03-12-11, 07:04 AM   #2
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If the lower end of the seatpost is below the bottom of the toptube you should be ok. If it intersects the toptube anywhere I wouldn't ride it that way. That minimum insertion depth of 63.5 mm seems quite short to me. Almost all of the seatposts I'm familiar with have their minimum insertion marks at least 75 mm above the end.
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Old 03-12-11, 07:56 AM   #3
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50mm MINIMUM past the lower edge of the top tube.
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Old 03-12-11, 08:12 AM   #4
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Quote:
Originally Posted by 1saxman View Post
50mm MINIMUM past the lower edge of the top tube.
Hmmm, given that even older "standard diameter" steel frames had 25.4 mm toptubes, the 63.5 mm minimum insertion depth doesn't give him near enough to work with if there should be 50 mm below the bottom of the top tube.

50+25 = 75 mm minimum and that assumes the top of the seattube is flush with the top of the top tube. It's even worse if the toptube has a larger diameter and/or the seattube projects above it.
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Old 03-12-11, 12:27 PM   #5
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On My touring bike to use My traditional Campagnolo 2 bolt seatpost,
which was to be at its Max height, I had another seat post [plain top Kalloy]
machined to match ID's in the overlap, and welded onto the older Campag Post ..
then, of course, weld machined down to the same OD.

I cut off the extra when it hit the Bottle boss in the front of the seat tube.
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Old 03-12-11, 05:34 PM   #6
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Originally Posted by fietsbob View Post
On My touring bike to use My traditional Campagnolo 2 bolt seatpost,
which was to be at its Max height, I had another seat post [plain top Kalloy]
machined to match ID's in the overlap, and welded onto the older Campag Post ..
then, of course, weld machined down to the same OD.

I cut off the extra when it hit the Bottle boss in the front of the seat tube.
I assume you are a competent welder and machinist or have friends who are and work for beer. What you are proposing would cost a fortune if it was done by a commercial machine shop. The OP doesn't even have a real Campy seatpost, just a knock-off. It's not worth modifying.
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Old 03-12-11, 05:45 PM   #7
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Quote:
Originally Posted by HillRider View Post
The OP doesn't even have a real Campy seatpost, just a knock-off. It's not worth modifying.
Exactly! Which is why I am not going to risk cracking my frame just so I can use the post. The post is only half way past the top of the top tube, basically intersecting with empty space in there.

Thank you for everyone's comments and suggestions!
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