HOT: Active* forum members generally gain 5% discount at starbike.com store!
Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Articles FAQ Contact About




Post new topic Reply to topic  [ 22 posts ] 
Go to page 1, 2  Next
Author Message
PostPosted: Tue Jan 08, 2013 12:57 pm 
Offline

Joined: Mon Dec 24, 2012 1:18 pm
Posts: 19
Hi all.

My first post here after lurking some time, but i thought that this must be something for carbon experts like you.

I was out looking at a lovely Look 595 ultra, but the frame have been cut to fit the former user, so if I have to fit it, I'm missing 1-1,5 cm under the stop limit at the seatpost. I have uploaded pictures below to illustrate the seatpost (that have several cuts/lose elements)

I need to tighten the seatpost right under the red spacer ~1cm under the stop.

I weight 65kg (with clothes), so is there any risk that i can damage the frame or seatpost?
Is it a go or no-go?


Image
Image
Image


Regards Lars


Top
 Profile  
 
PostPosted: Tue Jan 08, 2013 7:22 pm 
Offline

Joined: Mon Jan 02, 2006 7:10 pm
Posts: 338
Perhaps you could find a saddle with a particularly extended rails to seat distance? I dont know how much variation is out there and whether 1 cm is feasible, but anything you could do to lower the seatpost would lower the risk you are worried about.


Top
 Profile  
 
Posted: Tue Jan 08, 2013 7:22 pm 


Top
  
 
PostPosted: Tue Jan 08, 2013 7:28 pm 
Offline

Joined: Sun Oct 21, 2012 8:15 pm
Posts: 49
You could use lower the seat height by using shoes and pedals which give you a lower stack height.


Top
 Profile  
 
PostPosted: Tue Jan 08, 2013 7:32 pm 
Offline
User avatar

Joined: Thu May 04, 2006 4:43 pm
Posts: 5066
Location: Wherever there's a mountain beckoning to be climbed
I am not saying that this will necessarily be a good solution, but you can consider the Look "RePost"
http://www.lookcycle.com/en/us/route/accessoires/rsp.html
http://www.lookcycle.com/en/us/route/accessoires/rsp-r5.html .
I'll leave you to look into it further.


Top
 Profile  
 
PostPosted: Tue Jan 08, 2013 9:41 pm 
Offline
User avatar

Joined: Fri Jun 30, 2006 2:55 pm
Posts: 41
Location: Nashville, TN
To add to what was said by ghisallo2003, I've found variations of up to 1.75 cm from rail to top of saddle between the various road saddles I have.


Top
 Profile  
 
PostPosted: Tue Jan 08, 2013 9:54 pm 
Offline

Joined: Mon Dec 24, 2012 1:18 pm
Posts: 19
Okay that's a lot everybody!

Can anyone recommend a 'tall' saddle?

I have looked, but it's hard to see which ones that is 'tall' and which is not.

This eg.g look 'tall' but i honestly don't have any idea.
Selle italia x2 flow
Image


Top
 Profile  
 
PostPosted: Tue Jan 08, 2013 9:57 pm 
Offline

Joined: Wed Feb 03, 2010 1:31 am
Posts: 314
Maybe related, maybe not. I have a carbon Orbea frame with a carbon Profile Designs seatpost. The post is about 1 cm above the minimum insertion line. The minimum insertion line is about 1 cm above the seatpost clamp and visible. Using it a couple years like this.


Top
 Profile  
 
PostPosted: Tue Jan 08, 2013 10:41 pm 
Offline
User avatar

Joined: Fri Jun 30, 2006 2:55 pm
Posts: 41
Location: Nashville, TN
The lowest I've measured of the saddles I have is the Specilaized Romin. It measures a little over 4 cm from the bottom of the rail to the top of the saddle. The tallest I have is a Koobi Xenon which measures almost 6 cm. I have a couple MTB saddles which are even taller. Best bet is to use the saddle you made your initial measurement with as a baseline and head to your LBS and measure a few saddles.


Top
 Profile  
 
PostPosted: Wed Jan 09, 2013 9:53 am 
Offline

Joined: Mon Dec 24, 2012 1:18 pm
Posts: 19
I think the result must be a little over the stop and a new saddle.


Top
 Profile  
 
PostPosted: Thu Jan 10, 2013 5:24 am 
Offline
User avatar

Joined: Wed Sep 26, 2007 1:57 pm
Posts: 7408
Location: San Francisco, CA
It's an interesting question: if you weigh nothing and your saddle weighs nothing you only need enough seatpost in the frame for it to clamp. The heavier you are the more seatpost you need. At some point you have enough seatpost in there that it's no longer strength-limiting. But clearly 65 kg is less than the design limit of the post so being exactly at the line isn't a problem. But 1-1.5 cm is large.

My guess is the strength is proportional to the square of the amount of seatpost in the tube but a mechanical engineer would be able to answer that better.

_________________
http://djconnel.blogspot.com/
Fuji SL/1
\


Top
 Profile  
 
PostPosted: Thu Jan 10, 2013 6:03 am 
Offline
User avatar

Joined: Sat Aug 29, 2009 4:30 pm
Posts: 1483
I would have thought "no problem at all".
I think most seatposts recommend about 2.5" of minimum insertion, and I have run them with only about 1" of insertion.
Going 1-1.5 cm below the manufacturer's line seems pretty safe to me because the manufacturer typically includes a very conservative safety factor.
But this is just my opinion, and like all deviations from manufacturer's specs, it is 'At your own risk."
I happen to be a mechanical engineer, but I have applied no analysis whatsoever to this. Only gut feel and experience. :)


Top
 Profile  
 
PostPosted: Thu Jan 10, 2013 6:33 am 
Offline
User avatar

Joined: Thu Aug 25, 2005 7:09 pm
Posts: 1227
Location: In the industry
This baby will easily give you 3cm of extra height, but it's hideous (although it allows you to have children).

2.5" (6.25cm?) of grab is probably not enough. I have worked with quite a few bike engineers, and they mostly say 7-8 is required.

In fact, a manufacturer I know that uses internally butted seat tube with 2" of grab is having lots of warranty issues. Remember this is in Asia where 65kg dudes are pretty common.

Image

_________________
Fast falcons: http://www.youtube.com/watch?v=j3mTPEuFcWk" onclick="window.open(this.href);return false;
www.falcobike.com
Facebook: falcobikeglobal


Top
 Profile  
 
PostPosted: Thu Jan 10, 2013 9:56 am 
Offline
Formerly known as wassertreter

Joined: Tue Apr 12, 2011 8:08 am
Posts: 1851
Location: Pedal Square
djconnel wrote:
My guess is the strength is proportional to the square of the amount of seatpost in the tube but a mechanical engineer would be able to answer that better.

Probably closer to a log function I'd reckon, at some point the gain from more overlap diminishes.

_________________
Bikes: Raw Ti, 650b flatbar CX


Top
 Profile  
 
PostPosted: Thu Jan 10, 2013 2:55 pm 
Offline

Joined: Thu Sep 13, 2012 7:31 am
Posts: 17
Location: Slovenia
I have 2 friends with 695...
You can find a guy who works with carbon and he will make the seat-tube in height you need. It will be great if you have the piece which was cutted
It should not cost more then 50 euros and here our guy make it so good nobody can find where it was putted together


Top
 Profile  
 
Posted: Thu Jan 10, 2013 2:55 pm 


Top
  
 
PostPosted: Thu Jan 10, 2013 4:42 pm 
Offline
Shop Owner

Joined: Sat Jun 13, 2009 4:02 am
Posts: 1955
Location: NoVA/DC
Typically you want the insertion to be a minimum of 2.5x the diameter. That does little for you, with a non-round post. On conventional frames, an additional rule is for the bottom of the post to pass the bottom of the top tube.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 22 posts ] 
Go to page 1, 2  Next


Who is online

Users browsing this forum: Bing [Bot], Exabot [Bot], Google Adsense [Bot] and 42 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

   Similar Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Alchemy Hub Recall -- Stop using every ORC-UL

[ Go to page: 1, 2, 3, 4, 5 ]

in Road

nothingman

61

5444

Wed Jul 16, 2014 4:57 pm

Zigmeister View the latest post

There are no new unread posts for this topic. Cable stop replacement for Di2.

in Road

Thanh

1

209

Tue Jul 15, 2014 9:56 pm

Thanh View the latest post

There are no new unread posts for this topic. FINALLY got my Lightning cranks to stop creaking!

in Road

Chris_W

6

1111

Wed Oct 02, 2013 2:47 am

otoman View the latest post

There are no new unread posts for this topic. SOLVED - Head tube cable stop issue/problem

in Road

alanjob

14

693

Sun Oct 06, 2013 11:50 am

alanjob View the latest post

There are no new unread posts for this topic. Interesting S2 seatpost?

in Road

Getter

4

893

Mon Aug 19, 2013 7:47 am

Getter View the latest post


It is currently Thu Jul 31, 2014 5:26 am

All times are UTC + 1 hour




Advertising   –  FAQ   –  Contact   –  Convert   –  About

© Weight Weenies 2000-2013
hosted by starbike.com


How to get rid of these ads? Just register!


Powered by phpBB