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

Front Derailleur Cable Routing?

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.

Front Derailleur Cable Routing?

Old 09-02-12, 08:50 PM
  #1  
nolefan
Senior Member
Thread Starter
 
Join Date: Apr 2012
Location: Thomasville, GA
Posts: 69

Bikes: Trek 800/830

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Front Derailleur Cable Routing?

Ok, I have a stupid question regarding the routing of my Sora front derailleur cable in the pinch bolt.

1st - Please dis-regard the bad picture
2nd - Please dis-regard the frayed cable, it is going to be replaced which is what has spawned this question

In the picture, circled in yellow at the bottom of the pinch bolt, there is a "ledge". Should the cable be run through this, or is it correct as shown in the picture? If it doesn't need to routed through this "ledge", what is its purpose?

Thanks

nolefan is offline  
Old 09-02-12, 09:01 PM
  #2  
FBinNY
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 35,964

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 125 Post(s)
Tagged: 1 Thread(s)
Quoted: 4368 Post(s)
Likes: 0
Liked 40 Times in 35 Posts
The way you have it routed is correct. When you go to replace the cable you'll probably find a groove in the arm. As for the ledge, who knows? But if you routed the wire over it then down, you'd have a sharp bend which would flex as the arm moved, quickly fatiguing the wire.

Maybe the groove is a clever ploy to get people like post pictures and give the derailleur some free publicity.
FBinNY is offline  
Old 09-03-12, 12:04 AM
  #3  
Turtle Speed
happy bike wishes
 
Turtle Speed's Avatar
 
Join Date: Jun 2012
Posts: 265
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I'm glad someone else asked this question, because I saw that during some FD repositioning and I was going crazy trying to figure out what I was missing with its function. Apparently it's still a mystery, but if people more experienced are saying forget it, then I will too.
Turtle Speed is offline  
Old 09-03-12, 12:21 PM
  #4  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 15,169

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3011 Post(s)
Liked 1,335 Times in 934 Posts
The "ledge" on the arm is to correctly position the cable to maintain the actuation ratio. The cable will flex/bend at the end of the ledge and the dimension form this cable bend point to the arm's pivot will stay the same through the arm's movement/stroke.

This is the same reason why Shimano rear der cable ancher bolts have a pressure washer with a tab. the tab is to create a cable bending point and not to be an anti rotation device. I see a lot of gear cables improperly routed/attached at work. Saddly sometimes after other shops have done gear servicing...

Shimano has an inmense amount of instructional help available on line. Andy.
Andrew R Stewart is offline  
Old 09-03-12, 12:26 PM
  #5  
Andrew R Stewart 
Senior Member
 
Andrew R Stewart's Avatar
 
Join Date: Feb 2012
Location: Rochester, NY
Posts: 15,169

Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Raleigh Pro, Trek Cycle Cross, Mongoose tomac ATB, GT Bravado ATB, JCP Folder

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3011 Post(s)
Liked 1,335 Times in 934 Posts
I should add that changing the cable routing about the anchor bolt/pressure washer is a way to play with the actuation ratio. The "HUBBUB trick" uses this to try to have a Campy/Shimano mix work well. But these attempts to mix non compatible parts with mere cable attachment methods usually don't work well. Touchy and fine cable tension adjustments, shifting response drop off after a few shifts, chain run noise, auto shifting under power.

The Jtek Shiftmate is the best solution for these mismatched systems. To answer a question not asked... Andy.
Andrew R Stewart is offline  
Old 09-04-12, 02:44 AM
  #6  
TheRedWolf
Senior Member
 
Join Date: Oct 2010
Location: flat lands of Indiana
Posts: 70

Bikes: 2013 Wilier Gran Turismo; 2007 Specialized Sequoia; 2011 Bike Friday Pocket Sport (for traveling & touring)

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Originally Posted by Andrew R Stewart View Post
The "ledge" on the arm is to correctly position the cable to maintain the actuation ratio. The cable will flex/bend at the end of the ledge and the dimension form this cable bend point to the arm's pivot will stay the same through the arm's movement/stroke.

This is the same reason why Shimano rear der cable ancher bolts have a pressure washer with a tab. the tab is to create a cable bending point and not to be an anti rotation device. I see a lot of gear cables improperly routed/attached at work. Saddly sometimes after other shops have done gear servicing...

Shimano has an inmense amount of instructional help available on line. Andy.

Shimano does have a lot of help documents on line- but no pictures (only sketches) and cable routing is not addressed very well. I had this same problem (and many more, including cable routing to brakes), and neither Shimano or Park's sites had clear answers. BF's is often the best help.
TheRedWolf is offline  
Old 09-04-12, 05:03 AM
  #7  
nolefan
Senior Member
Thread Starter
 
Join Date: Apr 2012
Location: Thomasville, GA
Posts: 69

Bikes: Trek 800/830

Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
I agree with the wolf, Shimano has some great tech documents, but that part just isn't covered very well.

Thanks for the answers everyone!!!
nolefan is offline  
Old 09-04-12, 08:45 AM
  #8  
FBinNY
Senior Member
 
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 35,964

Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter

Mentioned: 125 Post(s)
Tagged: 1 Thread(s)
Quoted: 4368 Post(s)
Likes: 0
Liked 40 Times in 35 Posts
General rule for attaching cables to anchor nuts if the instructions are vague.

Unless there's a clear reason to do otherwise, the cable always goes to the distal (far) side of the anchor bolt.

The logic is fairly simple. The functional length is set by the distance from the cable to the pivot bolt. The object is to get the target leverage with the least use of material. There's no logical reason for a manufacturer to lengthen the pivot arm just so they can put the screw to the far side of the cable.

The other way to check for any particular component (brake or derailleur) is to see if there's a groove in the body, and to arrange the wire for the best fair led (straight approach) to the anchor. Parts makers don't intentionally introduce bends into a cable route, because that introduces unnecessary complications.

There is an exception. If, for some reason you want to increase cable response by about 10% because, for example, you're using chainrings with wider spacing than the original, you can route the cable to the near side which shortens the arm, and increases travel.

Last edited by FBinNY; 09-04-12 at 08:48 AM.
FBinNY is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
venturi95
Bicycle Mechanics
5
06-22-19 09:37 PM
MKIV987
Bicycle Mechanics
5
01-06-17 12:07 AM
corrado33
Bicycle Mechanics
4
01-10-16 04:24 PM
philbob57
Bicycle Mechanics
6
05-13-15 02:37 PM
jagerk
Bicycle Mechanics
3
04-10-12 07:58 PM

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.