Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

Seatpost shim question.

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

Seatpost shim question.

Old 09-23-16, 09:21 AM
  #1  
Full Member
Thread Starter
 
MrWasabi's Avatar
 
Join Date: Mar 2016
Location: Lutz, FL
Posts: 416

Bikes: 2014 Fuji Traverse 1.3, 2020 Electra Cruiser 1, 1995 Giant CFM-4

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 124 Post(s)
Liked 51 Times in 36 Posts
Seatpost shim question.

My bikes seat tube is 31.6 and I want to use a post that is 26.8. I'm having a hard time finding a 26.8-31.6 shim but have found a lot of 27.2-31.6 shims. If I go with the 27.2 is it going to be too loose even after I tighten things up?

Thanks for any input.
MrWasabi is offline  
Old 09-23-16, 09:49 AM
  #2  
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,355 Times in 862 Posts
Outside of Seat Post sizing shim, is Inside of seat tube diameter ..

Outside of seat post is the inside the Seat Post sizing shim,

Get the numbers to match .. If in fact the seat tube is 31.6.. Inside and you get the

31.6-27.2 shim and a 27.2 seat post?


If I go with the 27.2 is it going to be too loose even after I tighten things up?
Only, if you Dont use a 27.2 seatpost But insist on using the 26.8...





./.
fietsbob is offline  
Old 09-23-16, 09:55 AM
  #3  
Full Member
Thread Starter
 
MrWasabi's Avatar
 
Join Date: Mar 2016
Location: Lutz, FL
Posts: 416

Bikes: 2014 Fuji Traverse 1.3, 2020 Electra Cruiser 1, 1995 Giant CFM-4

Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 124 Post(s)
Liked 51 Times in 36 Posts
Originally Posted by fietsbob
Outside of Seat Post sizing shim, is Inside of seat tube diameter ..

Outside of seat post is the inside the Seat Post sizing shim,

Get the numbers to match .. If in fact the seat tube is 31.6.. Inside and you get the

31.6-27.2 shim and a 27.2 seat post?



Only, if you Dont use a 27.2 seatpost But insist on using the 26.8...


./.
Yes, the seatpost is marked 26.8, the manual for my bike says the seat tube is 31.6. The 26.8 seatpost is the one I want to use so I'll just continue to look for a 26.8-31.6 shim. I think I found one on eBay once the seller gets back.

Thanks for your input.
MrWasabi is offline  
Old 09-23-16, 10:11 AM
  #4  
Banned
 
Join Date: Jun 2010
Location: NW,Oregon Coast
Posts: 43,598

Bikes: 8

Mentioned: 197 Post(s)
Tagged: 0 Thread(s)
Quoted: 7607 Post(s)
Liked 1,355 Times in 862 Posts
You can Hire a Machine shop and they can custom make one for you, from a bar of Aluminum, on their Lathe.


Kalloy seat posts are cheap , why not just buy a 27.2?

A 1" .. 25.4 is also a common ID for Seat post sizing shims [Wheels & QBP, suppliers to bike shops]

so you can buy a 1" seat post..





Applying Simple Math .... 27.2 - 26.8=0.4 mm difference in diameter .. 2 steps undersize.

shim sheet stock use 1/2 that (radius) so 2mm thick shim stock wrapped around your 26.8 seazt post would bring it out to a measured 27.2, to then use a machined shim in that 27.2/31.6 size..




./.
fietsbob is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
kflagg
Classic & Vintage
13
06-19-14 04:16 AM
Grambo
Bicycle Mechanics
1
01-01-13 02:58 PM
timtak
Bicycle Mechanics
12
11-14-11 04:38 AM
maxmonster
Bicycle Mechanics
16
05-14-10 06:39 AM

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.