Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Tandem Cycling A bicycle built for two. Want to find out more about this wonderful world of tandems? Check out this forum to talk with other tandem enthusiasts. Captains and stokers welcome!

User Tag List

Reply
 
Thread Tools Search this Thread
Old 10-17-11, 10:18 AM   #1
mymojo
Senior Member
Thread Starter
 
mymojo's Avatar
 
Join Date: Mar 2011
Location: Plano, Texxas
Bikes: '10 Specialized Allez, '09 Cervelo S1, '93 Trek T200 (tandem), Rocky Mountain Metro 30
Posts: 517
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Capt' seatpost problem

I'm having a major issue with the captains seat post not staying in place!

OK, so I'm a Clyde, but still I don't have this issue on any of my other bikes. After a couple of miles it will twist a bit and then just start dropping. We've tried to tighten in - to the point of actually snapping a bolt - with no success. Short of drilling a bold hole through the tube, does anyone have any suggestions?
mymojo is offline   Reply With Quote
Old 10-17-11, 10:31 AM   #2
DubT
Senior Member
 
Join Date: Sep 2009
Location: Central Illinois
Bikes: Trek Speed Concept 9.9, 2011 Calfee Tetra Tandem
Posts: 1,038
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Try some carbon fiber assembly paste, it is kind of gritty and helped on my Trek Speed Concept when the seat post was slipping. It solved the problem. Most LBS have it.

Wayne
DubT is offline   Reply With Quote
Old 10-17-11, 10:32 AM   #3
diabloridr
Senior Member
 
diabloridr's Avatar
 
Join Date: Dec 2010
Location: Central Coast, California, USA
Bikes: Co-Motion Speedster, Calfee Dragonfly, Ancient Sun Fixie, Trek 5900, Trek 9800
Posts: 323
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
You might consider using a product such as Tacx Carbon Assembly Compound to create extra friction between the seatpost and the frame.
diabloridr is offline   Reply With Quote
Old 10-17-11, 12:38 PM   #4
steve53mg
Senior Member
 
Join Date: Dec 2009
Location: Long Island, NY
Bikes: Serotta Legend Ti, Santa Cruz Heckler, Santana Visa TAndem
Posts: 198
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Are you sure that you don't have a dimensional mismatch, or a stretched collar which is allowing the clamp to bottom out at the joint and not getting tight enough. Locktight makes a sleaving compound that might work, but might make the joint a little too permanent.
steve53mg is offline   Reply With Quote
Old 10-17-11, 12:44 PM   #5
waynesulak
Senior Member
 
waynesulak's Avatar
 
Join Date: Jan 2008
Location: Ft Worth, TX
Bikes: 650B tandem converted from Santana Arriva, Santana Noventa, Boulder Bicycle 700C, Gunnar Sport, Trek TX700,
Posts: 1,913
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
What are the bike type and seatpost size you are using?
waynesulak is offline   Reply With Quote
Old 10-17-11, 01:34 PM   #6
prathmann
Senior Member
 
Join Date: Nov 2008
Location: Bay Area, Calif.
Bikes:
Posts: 6,007
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
Quote:
Originally Posted by steve53mg View Post
Are you sure that you don't have a dimensional mismatch, or a stretched collar which is allowing the clamp to bottom out at the joint and not getting tight enough.
This would be my suspicion as well. On one of my bikes (a Trek MTB) the factory original seatpost is just a bit on the loose side and prone to slipping. Inserting a sleeve cut from a soda can cured the problem.
prathmann is online now   Reply With Quote
Old 10-17-11, 02:42 PM   #7
AllezDada
Senior Member
 
Join Date: Jan 2011
Bikes:
Posts: 162
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by diabloridr View Post
You might consider using a product such as Tacx Carbon Assembly Compound to create extra friction between the seatpost and the frame.
This solved the problem on my carbon road bike for me.
AllezDada is offline   Reply With Quote
Old 10-18-11, 09:03 AM   #8
bjjoondo 
Old, SLOW bike rider! ;)
 
Join Date: Nov 2008
Location: Colorado Springs, CO.
Bikes: 1993 Mongoose Switchback MTB
Posts: 1,856
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
OP, check with your LBS and see if they can, KNURL the post, the stroker seat post on our new Trek T-900 hybrid tandem was doing that and they had a way, (tool), to make a indenting gripping surface on the slick seat post, they called it "knurling" the post, FYI. Sorry photo is facing the wrong way but you can SEE the pattern the knurling tool put into the seat post, NO slippage at all now.
__________________
Take care, RIDE SAFE, have FUN!
B.J. Ondo
1993 Mongoose Switchback Ridged MTB, converted to a "Rail Trail Bike"! :)

Last edited by bjjoondo; 10-18-11 at 09:17 AM. Reason: added photo
bjjoondo is offline   Reply With Quote
Old 10-18-11, 10:24 AM   #9
tandem rider
Senior Member
 
Join Date: Dec 2005
Location: Indianapolis, IN
Bikes: Co-Motion tandem, Serotta, and Specialized mt. bike
Posts: 348
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Aluminum seat posts can indent from the tight seat post clamp. You may not be able to see the indentation but if you wet your fingers and run then down the seat post you can probably feel it. If you have calipers available you could measure for an indentation. Another possibility is a seat post slightly too small. If you had this problem from the beginning then the seat post may be too small in diameter even though it is marked the correct diameter. Trying another seat post to see if it slides down would answer that question. I would not drill a hole through the tube to put a bolt in. The top of the seat tube is a high stress area and you could break or bend the seat tube causing expensive damage to your frame. The compounds mentioned above could be used if the seat post is the correct size.
tandem rider is offline   Reply With Quote
Old 10-18-11, 12:00 PM   #10
ibis_ti
Senior Member
 
Join Date: Jul 2009
Location: Norcal
Bikes:
Posts: 201
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you get desperate, you can try a hose clamp or something like this:

http://www.origin-8.com/?page_id=91&...cl1=SEAT+POSTS
ibis_ti is offline   Reply With Quote
Old 10-18-11, 01:13 PM   #11
mymojo
Senior Member
Thread Starter
 
mymojo's Avatar
 
Join Date: Mar 2011
Location: Plano, Texxas
Bikes: '10 Specialized Allez, '09 Cervelo S1, '93 Trek T200 (tandem), Rocky Mountain Metro 30
Posts: 517
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
So Im thinking if I knurl the post, add a coke can shim, coat it in carbon paste and hold it all together with an Origin8 seat clamp i should be good!
mymojo is offline   Reply With Quote
Old 10-18-11, 05:19 PM   #12
zonatandem
Senior Member
 
zonatandem's Avatar
 
Join Date: Dec 2003
Location: Tucson, AZ
Bikes: Custom Zona c/f tandem + Scott Plasma single
Posts: 10,837
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 21 Post(s)
Alu beer or pop can shim works.
zonatandem is offline   Reply With Quote
Old 10-19-11, 04:34 PM   #13
Tom Spohn
Senior Member
 
Join Date: Aug 2011
Location: Seattle
Bikes: Spec. Roubaix, Cannondale RT2, BF NWT, BF tandem
Posts: 201
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
If you can get an aluminum can shim into the seat post it would pay to see if a larger post would work.
Tom Spohn is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 02:24 PM.