Go Back  Bike Forums > Bike Forums > Classic & Vintage
Reload this Page >

Should a 26.4 fork crown measure 26.4?

Notices
Classic & Vintage This forum is to discuss the many aspects of classic and vintage bicycles, including musclebikes, lightweights, middleweights, hi-wheelers, bone-shakers, safety bikes and much more.

Should a 26.4 fork crown measure 26.4?

Old 06-17-22, 07:50 PM
  #1  
Mr. Spadoni 
Senior Member
Thread Starter
 
Join Date: Jan 2015
Posts: 668
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked 196 Times in 108 Posts
Should a 26.4 fork crown measure 26.4?

My Stronglight X14 headset that was installed when it came from the builder has been giving me some problems. So I pulled it apart today. Issue is that the bottom cup somehow got dented. Dang, only 20 years use from it. As part of the replacement process, I pulled off the race, and measured the fork crown to see what would fit when I replace this headset. Crown was not particularly cleanly faced and …..it does not measure 26.4. Some places 23.8, sometimes less than that.
Question is…how exact does this need to be? Can I throw something in and expect that the load will keep it in place? Do I need some loctite? A shim?
suggestions?

Last edited by Mr. Spadoni; 06-18-22 at 07:45 AM.
Mr. Spadoni is online now  
Old 06-17-22, 08:06 PM
  #2  
juvela
Senior Member
 
juvela's Avatar
 
Join Date: Feb 2013
Location: Alta California
Posts: 12,030
Mentioned: 338 Post(s)
Tagged: 1 Thread(s)
Quoted: 2928 Post(s)
Liked 1,552 Times in 1,125 Posts
-----


the convention/rule of thumb is that the seat should be .1mm larger in diameter than the I.D of the race

you mention Stronglight

on the V4 model for example the crown race has a stepped inner face so that the seat must be a low one


-----
juvela is offline  
Old 06-17-22, 10:35 PM
  #3  
Mr. Spadoni 
Senior Member
Thread Starter
 
Join Date: Jan 2015
Posts: 668
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked 196 Times in 108 Posts
Here’s the headset in question. Can’t seem to locate the model. And I mistyped the crown diameter . It’s 26.3, not 23.8


Mr. Spadoni is online now  
Old 06-18-22, 05:34 AM
  #4  
juvela
Senior Member
 
juvela's Avatar
 
Join Date: Feb 2013
Location: Alta California
Posts: 12,030
Mentioned: 338 Post(s)
Tagged: 1 Thread(s)
Quoted: 2928 Post(s)
Liked 1,552 Times in 1,125 Posts
Originally Posted by Mr. Spadoni View Post
Hereís the headset in question. Canít seem to locate the model. And I mistyped the crown diameter . Itís 26.3, not 23.8


-----

thank you

this figure makes more sense

there are two main standards for fork crown race i.d. and fork crown race seat diameter

they are 26.5mm and 27.0mm for fork crown race i.d.

"in general" quality sets employ the 26.5 and "ordinary" sets employ the 27.0

suggest first step should be to get the fork crown milled to eliminate this variable as a possible source of difficulty

it is OK to shim when needed; care must be taken not to permit the shim stock to get under the race in the seating process

another technique employed where the distance is very small is to use a centre punch and mallet to make indentations evenly spaced around the vertical surface of the seat

each indentation creates a tiny parapet which very slightly increases the effective diameter of the seat

-----
juvela is offline  
Old 06-18-22, 09:10 AM
  #5  
JohnDThompson 
Old fart
 
JohnDThompson's Avatar
 
Join Date: Nov 2004
Location: Appleton WI
Posts: 23,745

Bikes: Several, mostly not name brands.

Mentioned: 142 Post(s)
Tagged: 0 Thread(s)
Quoted: 3045 Post(s)
Liked 2,170 Times in 1,295 Posts
Looks like a Stronglight X12 unit.

Crown race diameter of 26.3mm isn't that far off ISO 26.4mm, and should provide a decent interference fit. I assume that the race was properly seated and functioning before you removed it. What does the race seat on the fork measure?
JohnDThompson is offline  
Old 06-18-22, 12:25 PM
  #6  
Mr. Spadoni 
Senior Member
Thread Starter
 
Join Date: Jan 2015
Posts: 668
Mentioned: 15 Post(s)
Tagged: 0 Thread(s)
Quoted: 247 Post(s)
Liked 196 Times in 108 Posts
Thanks for the ID.
Properly seated? Well, the only other time I had this HS apart, the crown race slid off the steerer when I tripped the fork to take off the bearings. That didnít seem right, but the HS worked okay afterwards, until it started to bind. On their disassembly, I noticed a dent in the cup, which you can see in the first photo at about 5.30. How that got there is unknown but I am good at breaking things.
The fork measures between 26.4 and 26.28, depending on where I measure. As you can see from the second photo, itís not the cleanest finish Iíve encountered.


Mr. Spadoni is online now  
Old 06-19-22, 10:14 AM
  #7  
repechage
Senior Member
 
Join Date: Jun 2006
Posts: 17,782
Mentioned: 117 Post(s)
Tagged: 0 Thread(s)
Quoted: 2533 Post(s)
Liked 1,462 Times in 1,103 Posts
The lower cup ding can be filed back or nudged out.
the crown race seat...
already borderline too small
I would suggest hand knurling it- stein makes such a tool
or taking a cold chisel and tapping in a series of doinks aligned with the steerer axis.
16-24 equally spaced. Should grow the OD enough to set the crown race.
repechage 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 My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.