Go Back  Bike Forums > Bike Forums > Framebuilders
Reload this Page >

Aero seat post fix . Good idea bad idea ?

Notices
Framebuilders Thinking about a custom frame? Lugged vs Fillet Brazed. Different Frame materials? Newvex or Pacenti Lugs? why get a custom Road, Mountain, or Track Frame? Got a question about framebuilding? Lets discuss framebuilding at it's finest.

Aero seat post fix . Good idea bad idea ?

Old 05-25-23, 02:38 PM
  #1  
Aerotuned
Newbie
Thread Starter
 
Join Date: May 2023
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Aero seat post fix . Good idea bad idea ?

Hello .
Iíve a teardrop carbon aero seat post , broke the head off through my own roughness.
problem is the bike company have gone and the seat post is incredibly hard to get, carbon repair shop has said no to a fix ,
Itís 42mm longest point and 20mm wide section
just thinking would it be safe to buy a slightly bigger aero seatpost 48mm x 25mm to slip over the old down as far as the post clap . Mark position and liquid resin bond the 2 together by pouring fibreglass resin inbetween the gap of both ? Good idea or silly
Aerotuned is offline  
Old 05-25-23, 03:22 PM
  #2  
79pmooney
Senior Member
 
79pmooney's Avatar
 
Join Date: Oct 2014
Location: Portland, OR
Posts: 11,791

Bikes: (2) ti TiCycles, 2007 w/ triple and 2011 fixed, 1979 Peter Mooney, ~1983 Trek 420 now fixed and ~1973 Raleigh Carlton Competition gravel grinder

Mentioned: 120 Post(s)
Tagged: 0 Thread(s)
Quoted: 4129 Post(s)
Liked 3,086 Times in 2,010 Posts
Both posts CF? If so I'll bet the larger post will need significant cleanup inside (ie sanding and filing) to slip over the broken post but I don't see why it is not doable in concept. Use epoxy, not a polyester based resin. Be aware the epoxies "flow" as part of the cure cycle. That flow is wonderful for filling gaps but that epoxy will find a way to split the scene it you give it an avenue. (Dependent on how thick the epoxy is, warmth both generated in the cure and added from the outside and setting time.) Taping the joint ends with masking tape will do a lot to keep the epoxy behaved and will lift off after cure.

Safety-wise - if you bring the joint down to say 5mm above the clamp I cannot see anything worse happening than the seat slipping down that 5mm if all goes to heck. (Assuming you are road riding and not all out extreme BMXing.)

Another thought - that I've had before but never saw a way around: I like my seatpost set so the nose of the seat is almost a cm to the left. Always saw the aero posts that slid into aero seat tubes as a big compromise for me. But! with your proposal, I could twist the outer post slightly askew and set the seat right where I want it!
79pmooney is online now  
Old 05-25-23, 03:36 PM
  #3  
Aerotuned
Newbie
Thread Starter
 
Join Date: May 2023
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
yes both are CF posts and thanks I was going to use a polyester resin as we have it at work for flat roofing Iím sure it would be ok ? . Iíve roughed up the outside of the small seatpost ready for the over slip . Tape the end as you said . Iím not 2 concerned about the weight anyway , more the fact it was only my second ride on the bike after buying 😂 and not dumping a £1k bike
Desperate measures got me thinking
Aerotuned is offline  
Old 05-25-23, 04:20 PM
  #4  
Canaboo
Full Member
 
Join Date: Dec 2009
Posts: 482
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 10 Times in 10 Posts
You don't want to use polyester resin. Can we see a pic? Practically any carbon fail is repairable. When people say no immediately I would question their repair ability.
Canaboo is offline  
Likes For Canaboo:
Old 05-25-23, 05:35 PM
  #5  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 17,312

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3879 Post(s)
Liked 3,099 Times in 1,894 Posts
Your idea sounds like a possible fix if done well. Make sure there's a lot of surface contact area. Whatever epoxy you use will have a suggested joint gap for best results. Typical for this stuff (ill fitting parts) is that a few spots will be just right and a lot more won't be, so having a lot of overlap will help the numbers. I like the use of tape as a dam for seeping epoxy, done the same decades ago in the ski shop world fixing skies.

Depending on the fit of the "new" post over the "old" I might consider a building up of the old's top to better fill the new's ID. Fiberglass, carbon fiber ribbon come to mind. By holding the old post in the frame one could file down the added layers fairly easily and reduce the gaps. Relying on the epoxy only to fill gaps much larger than parts of a MM is a poor idea. I have heard of people mixing into the epoxy fibers, short cuts of glass or carbon, to better fill the gaps. I would only suggest a slow curing epoxy to give you time to handle/assemble the two posts. Can you give us an aprox amount of overlap between length the two posts?

A seat post failure is one of the lesser concerns I would have when riding. Although I will say riding a seatless bike is a lot harder than most would initially think Seriously we're not talking about highly stressed and structural frame or wheel parts. Broken bars, pedal spindles or cranks are usually a far worse thing to have happen. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 05-25-23, 10:42 PM
  #6  
Aerotuned
Newbie
Thread Starter
 
Join Date: May 2023
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Unfortunately I canít post pics as not 10 posts in yet 😂 itís broken right where the post and seat clamp section meet . So I pulled the half round saddle bit clean away from the post. Itís a v narrow post , 42mm long 20mm wide to 5mm wide safety first in the carbon guys eyes

The new post Iíve bought should have around 4mm of play in most areas with more towards the front of the tear drop .
its a Dassi aero bike . Think Iíll stick to mass production bikes in future
Aerotuned is offline  
Old 05-26-23, 07:44 AM
  #7  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 17,312

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3879 Post(s)
Liked 3,099 Times in 1,894 Posts
Originally Posted by Aerotuned
Unfortunately I canít post pics as not 10 posts in yet 😂 itís broken right where the post and seat clamp section meet . So I pulled the half round saddle bit clean away from the post. Itís a v narrow post , 42mm long 20mm wide to 5mm wide safety first in the carbon guys eyes

The new post Iíve bought should have around 4mm of play in most areas with more towards the front of the tear drop .
its a Dassi aero bike . Think Iíll stick to mass production bikes in future
If I might suggest the issue is the non common and round post, not the bike brand. While the brand did offer the bike with it's aero post no one forces anyone to actually buy it. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 05-26-23, 08:38 AM
  #8  
Aerotuned
Newbie
Thread Starter
 
Join Date: May 2023
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Andrew R Stewart
If I might suggest the issue is the non common and round post, not the bike brand. While the brand did offer the bike with its aero post no one forces anyone to actually buy it. Andy
True but to stick to more long running companyís may be a better option
Aerotuned is offline  
Old 05-26-23, 03:00 PM
  #9  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 17,312

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3879 Post(s)
Liked 3,099 Times in 1,894 Posts
Originally Posted by Aerotuned
True but to stick to more long running companyís may be a better option

Which won't eliminate the unique post shape unless you also eliminate their models that do use an aero post. It seems to me that a big aspect of this thread is the unique post shape, not the brand. Any brand can and does change specs periodically and will at some point to no longer support their older designs. This would have the same result, as the company going out of business, when their aftermarket parts are no longer available. Andy
__________________
AndrewRStewart
Andrew R Stewart is offline  
Old 05-27-23, 07:01 AM
  #10  
Canaboo
Full Member
 
Join Date: Dec 2009
Posts: 482
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 42 Post(s)
Likes: 0
Liked 10 Times in 10 Posts
Make a few more posts and get that picture up. There are plenty of gelled Epoxies that will fill gaps and not run out of a joint.
Canaboo is offline  
Old 05-27-23, 07:14 AM
  #11  
CrowSeph
Senior Member
 
CrowSeph's Avatar
 
Join Date: Mar 2016
Location: South Italy
Posts: 849

Bikes: BMC SLR01; Cannondale Trail; Robur 1956 ; Tomasini 1976 ; Chiorda Condorino 1974 ; Frejus/Rola 1937 ; Specialized RockHopper 1990

Mentioned: 10 Post(s)
Tagged: 0 Thread(s)
Quoted: 246 Post(s)
Liked 132 Times in 81 Posts
Can you post some photos?
CrowSeph is offline  
Old 05-27-23, 07:36 AM
  #12  
unterhausen
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 23,456
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 2,962 Times in 2,035 Posts
Upload your pictures to an album in your gallery. Let us know and we'll post them here for you. Don't forget to click the "upload" link on the upper right of the dialog box
unterhausen is offline  

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


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell or Share My Personal Information -

Copyright © 2023 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.