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  [ 12 posts ] 
Author Message
PostPosted: Sun Dec 09, 2012 3:21 pm 
Offline

Joined: Thu Jan 13, 2011 4:04 pm
Posts: 508
Location: Sunny UK
If you have fitted a lightweight alloy seatpost clamp with a Ti bolt and a carbon fibre seatpost, you may find that even when done up tightly and with carbon paste, the post still slips. :twisted:

You can tighten the bolt further but there is risk of either snapping the bolt, rounding off the hex head, stripping the thread in the clamp, or crushing the seatpost.

Having had this problem, looking at the clamp it is clear that as the clamp is tightened, the clamp ends are getting bent so the gap between then is not longer parallel. The force applied is bending the clamp instead of applying it to the seat tube and post.

To over come this, I have fitted a 0.5 mm washer in the gap so the ends of the clamp are no longer being bent and the force is bringing the ends nearest the seat tube together thus applying it to the seat tube. Obviously the thickness of the washer has to be chosen so that it does not prevent the clamp from being tightened. :thumbup: (it also prevent the clamp from being over tightened)

The photo shows that the gap is almost parallel, there is a slight gap between the washer and the clamp nearest the seat tube - if the washer was not there, then ends furthest away from the seat tube would be would be almost touching.


Attachments:
DSC08279.JPG
DSC08279.JPG [ 136.24 KiB | Viewed 1319 times ]
Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 3:50 am 
Offline

Joined: Wed Feb 09, 2005 4:51 am
Posts: 1625
It sounds counter-intuitive but flip the clamp bolt towards the front of the frame instead if the slit of the frame is at the back. It will allow for a more even distribution of clamping force.


Top
 Profile  
 
Posted: Mon Dec 10, 2012 3:50 am 


Top
  
 
PostPosted: Mon Dec 10, 2012 4:08 am 
Offline
Shop Owner

Joined: Sat Jun 13, 2009 4:02 am
Posts: 1951
Location: NoVA/DC
Agree that flipping the clamp can help it keep its shape. Doing so usually requires more torque to tighten, so it might be a win/lose. If you do try it, grease between the clamp and frame so one may slide against the other as each respective gap closes.


Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 4:25 am 
Offline
User avatar

Joined: Thu Mar 17, 2005 3:25 am
Posts: 2174
Location: Southern Indiana USA
Brilliant!

_________________
For certain parts stiffer is more important than lighter.


Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 4:41 am 
Offline

Joined: Wed Feb 09, 2005 4:51 am
Posts: 1625
thisisatest wrote:
Agree that flipping the clamp can help it keep its shape. Doing so usually requires more torque to tighten, so it might be a win/lose. If you do try it, grease between the clamp and frame so one may slide against the other as each respective gap closes.


Thanks for adding that important bit which I missed out on. :thumbup:

The application of grease between clamp and frame is important. :smartass:


Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 5:02 am 
Offline
User avatar

Joined: Thu Mar 17, 2005 3:25 am
Posts: 2174
Location: Southern Indiana USA
I already flip my clamps and put grease "approved by S&S cycles" but I still tend to have problems because if like to use shims to get down to 27.2 so I can use the Cannondale Save seatposts on my mountain bikes. I have been solving the problem by buying Salsa seat clamps which are heavy duty (and turning them around and greasing them with super grease). But this adds another great tool to the toolbox for solving this problem.

Also, I have not been very happy with TACX carbon "grease". It seems to deteriorate rapidly. I have been using never sieze on steel frames with carbon posts, and very small amounts of regular grease with aluminum frames with aluminum shims with carbon posts.

_________________
For certain parts stiffer is more important than lighter.


Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 4:48 pm 
Offline

Joined: Mon Feb 20, 2012 7:56 pm
Posts: 11
maxxevv wrote:
It sounds counter-intuitive but flip the clamp bolt towards the front of the frame instead if the slit of the frame is at the back. It will allow for a more even distribution of clamping force.

Very true!
A little bit of carbon assembly compound or a tiny bit of Loctite 609 rubbed on the insider edge could help if the reverse clap doesn't do it.


Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 6:52 pm 
Offline

Joined: Fri Oct 07, 2011 2:08 pm
Posts: 1365
Easy solution ....Just put a little bit of clear coat on your seatpost so it fits tight. Your seat post will not slip and you will not have to tighten your clamp so hard . Works every time .


Top
 Profile  
 
PostPosted: Mon Dec 10, 2012 11:34 pm 
Offline

Joined: Thu Jan 13, 2011 4:04 pm
Posts: 508
Location: Sunny UK
.... actually one of the clamps that I am using with a washer is a Cannondale, which has a little bump so can only be fitted so the gap in the clamp is on the opposite side to the seat tube gap.

I put a small mark with tippex on the seat post then tighten the seatpost bolt by feel whcih may well be less than the recommend setting since I do not have a torque wrench. With Ti bolts you can do them up tight then you can feel the bolt twisting but not actually screwing into the clamp - this is the point where I stop or even back up a fraction; and if the post slips, the washer comes in to save the day.

I am not sure I would like to use the lacquer method since that may help the post sezie in the frame - I had a nightmare time removing a Look carbon post from my Bianchi frame.


Top
 Profile  
 
PostPosted: Tue Dec 11, 2012 10:30 am 
Offline

Joined: Fri Oct 07, 2011 2:08 pm
Posts: 1365
I use carbon paste as well ....the seatpost comes out fine . Clear coat will not make any difference as seat posts have clear coat on them anyway . I have used this method on my Guru and Trek with no issues .


Top
 Profile  
 
PostPosted: Sun Jan 13, 2013 12:21 am 
Offline

Joined: Sun Oct 30, 2011 5:25 pm
Posts: 128
Location: London, UK
Useful thread - the more tips the better! Has anyone stopped aluminium posts slipping using the clearcoat trick (specifically a Thomson Masterpiece)?


Top
 Profile  
 
PostPosted: Mon Jan 14, 2013 1:21 pm 
Offline

Joined: Wed Jan 18, 2012 4:23 pm
Posts: 405
Location: Midlands, United Kingdom
I use carbon grip paste on alloy posts when they are smooth, I also have an ITM which has a recent rough surface so never slips....

_________________
Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956


Top
 Profile  
 
Posted: Mon Jan 14, 2013 1:21 pm 


Top
  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 12 posts ] 


Who is online

Users browsing this forum: doccoraje and 11 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. Lightweight seatpost clamp

in Road

vitriol

10

1011

Wed Oct 02, 2013 1:43 pm

Ceebers1 View the latest post

There are no new unread posts for this topic. Light Weight Seatpost Shim and Seatpost Clamp ?

in MTB

Scott35

6

765

Thu Apr 25, 2013 5:16 am

gifted child View the latest post

There are no new unread posts for this topic. overtighened seatpost clamp. damaged seatpost.

in Road

odin99

9

1569

Tue May 07, 2013 8:09 pm

btompkins0112 View the latest post

There are no new unread posts for this topic. Your take on Mcfk seatpost & seat-clamp?

[ Go to page: 1, 2 ]

in Road

Limbo

19

909

Wed Jan 01, 2014 4:27 pm

DMF View the latest post

There are no new unread posts for this topic. CarbonCycles Seatpost Clamp Assembly

in For sale - Pictures are mandatory 22-3-13

drainyoo

0

180

Sat Feb 22, 2014 8:04 pm

drainyoo View the latest post


It is currently Thu Apr 17, 2014 2:55 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