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

Front derailleur braze-on

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.

Front derailleur braze-on

Old 12-04-23, 07:52 AM
  #1  
Senior Member
Thread Starter
 
Join Date: Dec 2019
Posts: 953
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times in 212 Posts
Front derailleur braze-on

I have a braze-on front derailleur so am planning to make or buy the hanger that goes on the frame and braze it on. Does anyone know the standard for where it's supposed to go? Obviously I'll make sure the derailleur I have fits but it would be better to stick to any published standards if possible (in case the owner of the bike wants to try different chainrings etc. and runs out of wiggle room).
guy153 is offline  
Old 12-04-23, 11:34 AM
  #2  
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,383
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,683 Times in 2,507 Posts
I don't think there is a standard exactly. I think that page of the shimano frame requirements might be online
unterhausen is offline  
Likes For unterhausen:
Old 12-04-23, 12:41 PM
  #3  
framebuilder
 
Join Date: Dec 2009
Location: Niles, Michigan
Posts: 1,469
Mentioned: 50 Post(s)
Tagged: 0 Thread(s)
Quoted: 614 Post(s)
Liked 1,911 Times in 653 Posts
Eric is right there are too many different kinds of front derailleurs to have a standard. And of course their height changes based on how many teeth the front chainring has. Even Shimano's Dura Ace had a different height depending on the year. I have a very long list of front derailleur heights based on who the manufacture was and the year it was made.

To be safe you will want to mock up the position before brazing it on. That means installing the BB and crank and then placing the front derailleur where it is supposed to go compared to the chainring size and then marking that position. Don't forget that position is not only its height but also rotation.

I would definitely encourage buying an IC braze-on. I like the top of the derailleur part that attaches to the boss to be at the same height as the top of the boss. That just looks right to me. Because what chainring size I use may get smaller and how much the front derailleur height changes based on model and year, I didn't like to use a braze-on front derailleur boss. For example the old heights based on a 53 front chainring may or may not work with a compact crank and even if it does, it looks silly to have the derailleur at the far end of the slot. Of course if neither the chainring size or FD aren't going to change, a braze-on front derailleur looks nice and clean.
Doug Fattic is offline  
Likes For Doug Fattic:
Old 12-04-23, 01:23 PM
  #4  
blahblahblah chrome moly
 
bulgie's Avatar
 
Join Date: Apr 2009
Location: Seattle
Posts: 1,984
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1172 Post(s)
Liked 2,565 Times in 1,072 Posts
Two small points to add:

Remember that the der. cage rises up as it moves outward, so the height of the cage has to be measured with the parallelogram extended outward. Undoing the spring can help with some models; others don't allow that or not easily. you might have to rig up a cable and shifter if you want to be precise.

Be aware that the brazing heat, applied to only one side of the seat tube, will curve that tube a bit. If you're a stickler for perfect alignment, it means you can't use a "frame stick" or string method for centering the rear dropouts, unless you account for the bow in the middle of the tube. Other than that, it doesn't affect function, so most people ignore it, but I feel it's worth being aware of at least.

Would you consider the clamp-on part that gives the interface for a braze-on derailer? Looks a bit like a kluge, but it keeps all your options open for chainring size, derailer brand etc. Some of the clamps available are better looking than others, sorry I don't remember which ones I liked.
bulgie is offline  
Likes For bulgie:
Old 12-04-23, 03:41 PM
  #5  
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,383
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,683 Times in 2,507 Posts
clamp on adapters are a good idea. Unfortunately they don't make them for 27.2 anymore
unterhausen is offline  
Likes For unterhausen:
Old 12-04-23, 04:32 PM
  #6  
Senior Member
Thread Starter
 
Join Date: Dec 2019
Posts: 953
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 321 Post(s)
Liked 261 Times in 212 Posts
Thanks for all the advice! I could just get a clamp, but it's an unusually large seat tube (32.7mm OD). I was planning to TIG braze a tab on with basically a fillet on each side so it probably won't warp the tube (TIG brazing is very gentle with the heat input). I do have the derailleur and have ordered the chainrings and BB so I can make sure everything fits and then I guess I'll basically put it roughly in the middle of the range as it's a 50T big ring, which is itself middle of the range (sometimes people use a 46 or a 53).
guy153 is offline  
Old 12-04-23, 06:03 PM
  #7  
Randomhead
 
Join Date: Aug 2008
Location: Happy Valley, Pennsylvania
Posts: 24,383
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked 3,683 Times in 2,507 Posts
I like to use a 46. So I put them a little lower than other people. It's a balancing act
unterhausen is offline  
Likes For unterhausen:
Old 12-05-23, 08:06 AM
  #8  
Full Member
 
Join Date: Dec 2003
Posts: 447
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 13 Post(s)
Liked 45 Times in 10 Posts
Originally Posted by unterhausen
clamp on adapters are a good idea. Unfortunately they don't make them for 27.2 anymore
27.2?!

https://richardsachs.com/product/peg...6mm-f-c-clamp/
__________________
Atmo bis
e-RICHIE is offline  
Old 12-05-23, 01:38 PM
  #9  
blahblahblah chrome moly
 
bulgie's Avatar
 
Join Date: Apr 2009
Location: Seattle
Posts: 1,984
Mentioned: 92 Post(s)
Tagged: 0 Thread(s)
Quoted: 1172 Post(s)
Liked 2,565 Times in 1,072 Posts
That is a nice lookin' part, thanks for the link.
bulgie is offline  
Likes For bulgie:

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.